Personally I think an alliance with the US is rather, well I wouldn't say ASB, but rather improbable. Dewey is not nearly as anti-German as FDR was, and IIRC America has links to the German oil, steel, and automobile industries. And there's still the isolationist bloc to consider. I've no doubt they've shrunk, what with the US naval expansion and 'cash and lift', but they're still there. The closest I can see to an alliance would be a defensive alliance, as in the US wouldn't be obliged to join the war if the British declare war on anyone, though they would be if someone declared war on Britain. Even then it'd be a fight in the US Congress, both to accept an alliance and ratify a declaration of war (more so the latter).
Going to a peace treaty between Britain and the Axis, either Churchill has to step down on his own accord or forced out of office before negotiations begin. I agree though with Crimson King on this: Britain doesn't really need a 'win' to negotiate on even terms. The blockade alone is enough. However the terms of the treaty are going to be tricky. For starters certain terms of the Second Treaty of Versailles will prove...troublesome. Starting with the Low Countries, Belgium is in risk of being divided, considering the agreed-upon plebiscites in Wallonia and Flanders, which if won by France and the Netherlands sees the two provinces going to the respective victors. North Africa and the Med are fait accompli by this point, the territorial changes there - Morocco and Gibraltar to Spain, Tunisia, Malta, and Egypt to Italy - plus Axis dominance in the theater leave the British no choice. Central and West Africa are different: Britain will probably have to accept French control of the (former) Belgian Congo, but the British colonies in West Africa - implicitly recognized by France's Axis allies as French SOI - are a different matter. Most likely they'll stay with Britain for now, but in the interests of Axis unity the implicit French claims over them as enshrined within the Second Treaty of Versailles will remain...and an indicator that this is no peace, but an armistice with the two sides glaring at each other, waiting warily for the figurative knife in the back, and each sharpening their respective knife for the first such opportunity.
I have to stress this out: it is critical for France and Italy to stay German allies. And that means supporting their claims over key territories to make their being German partners seem more attractive than siding with Britain. Germany's great enemy is still the USSR after all, but if they can keep France and Italy alongside, Germany can focus itself and the East European allies (Romania, Hungary, Poland - they'll probably get back lost territory from the Soviets - and Finland, Greece and Yugoslavia, possibly Turkey) against the Soviets, and leave the Western and Mediterranean Fronts to the French and the Italians. Oh they'll need some support (Greece and Yugoslavia can help in the Med too), but this iteration of the Third Reich being what it is at least Germany wouldn't have to prop them up.
And speaking of the Soviet Union, Germany has bought some time in the event of peace with Britain to catch its breath and prepare. I don't know if the Germans know about the T-34, but even if they don't and development of the Panther and Tiger proceed normally, I can see Germany still up-gunning the Panzer IV to maintain its edge. IIRC the Panzer IV's up-gunned variants were able to match the T-34, and in light of that I suggest phasing it out slowly. Proportionately-decrease production of Panzer IVs and increase the production of Panthers as armored divisions are reequipped with the new tanks. Stugs should be kept in production, though decreased to a point: Tigers are good for first-echelon units, but considering how expensive heavy tanks are, it might be more economical to substitute Stugs for Tigers in second-echelon and reserve units.
The Luftwaffe's new aircraft were mentioned in the earlier article about mass production, with the Fw-190 slowly replacing the Me-109 from the Battle of France onwards, and the Ju-88 and Ju-87 being slowly phased out with newer, more-advanced models from the invasion of the Soviet Union onwards as well. Someone mentioned Type-XXI U-boats replacing the Type-VII, all of which is good, but I suggest doing it steadily, and not rushing it like IOTL. Sending out flawed machines onto the battlefield is a waste of money and resources, probably costing more than waiting to finish development properly before putting them into production.
Connected to this is mechanization of the German motorized divisions. Preferably it can be started before war starts, but if not, slowly phase the motorized divisions out of the first-echelon to the second-echelon and reserves. There's no need to rush, the motorized divisions are serviceable as they are.
However, while new technology is good (the German battlecruisers currently based in French ports also need to be constantly kept up to date*), the most important part of invading the Soviet Union is C3I. Command, Control, Communications, and Intelligence: the last part seems well-handled by Heydrich, and while I don't doubt British Intelligence and the NKVD will eventually crack some of the Axis codes just keeping pace should be enough. C3 is very important though, AFAIK the OTL Axis' activities were significantly-miraculous considering the chaos and anarchy of the Axis C3I IOTL. A dry run has already been conducted in the campaign against Britain, with the Franco-German distraction operations along the Channel Coast, the Franco-German-Italian-Spanish naval operations and siege of Gibraltar, the French operations in Africa, and the German-Italian operations in North Africa and the Med. Now those have to be expanded further: the Axis should review their AARs twice if not thrice or more, find and correct their mistakes, and improve what can and should be improved.
Connected to this is Japan: Japan can be a useful ally, but a dangerous one as well, as their ambitions risk a war with both the Soviets and the US at once - a fatal prospect. Now war with America is an implicit eventuality, but should be done after the Soviet threat has been neutralized. To that end Germany should 'bribe' Japan into going north, and be content (for now) with bases in Indochina in SE Asia. The bribe would take the form of technology, such as assistance in adopting assembly line mass production and improved armor. Like say, chassis, guns, and schematics for the Panzer IV, seeing as the Panther and Tiger are already going into mass production. As mentioned by a fellow AH member, Japan can easily make their own Stug-equivalents with the Chi-Ha chassis, they just have to mount a 7.5cm fixed gun and a sloped glacis plate. To get the most out of this, German trainers also need to help the Japanese bring their tactical doctrines up to speed, and with assembly line mass production of Japanese SMGs (serviceable IIRC IOTL just never produced en masse) and trucks Japan would have the motorized divisions needed to support the armored divisions.
Territory-wise Japan should stay out of Kamchatka: too close to the US, and stressing Japanese logistics to the limit. Even with assembly line mass production, Japan probably wouldn't have a large stock of trucks like the Germans, who've been pumping them out years before the war started, to say nothing of limited ports (to say nothing of Japan's merchant marine) and rail systems in Kamchatka. Sakhalin, the Maritime Province, and Khabarovsk should be Japan's focus, with a stake in the Siberian puppet they and the rest of the Axis would probably establish.
*Germany's battlecruisers don't need to go back to Germany for refitting. Move by rail the parts and specialists, and use the French yards to refit them. The French would probably learn something from it, but letting them do so as an informal arrangement/concession would make for a sign of trust between allies, just like Germany entrusting to them the Western Front. The British would probably mock it and think it an opportunity, but if Germany treats the French well then between the British 'sneak attack' on the French Navy, and the free hand the Germans are letting the French have in Africa (whereas the British would insist on preserving the status quo) the French would more likely want to kick British ass than stab Germans in the back. And speaking of that, here's another way to help further bind France to Germany: hold a plebiscite in Elsass-Lothringen. No doubt the French-speaking parts will go back to France, but the German-speaking parts will stay with Germany. A gentleman's deal to honorably settle the breach between the two powers once and for all, though it can be done after the war, with the afterglow of victory helping ease it along.
EDIT: someone mentioned Jim Crow x2 treatment for Jews, and IIRC Jewish scientists are working on Germany's nuclear weapons program. However under Jim Crow blacks could serve in the US military, they just couldn't be officers (AFAIK). Is this the same for Germany? IIRC Manstein (I'm not sure but I remember a German flag officer over this) IOTL protested the removal/persecution of Jews in the military, and that military service was already a mark of loyalty to Germany as it were.