I find the idea that a neutral Italy will free up British resources (manpower, airpower and naval power) doubtful. Arguably, Italy being neutral will force Britain to keep a constant presence on her borders as a result of their fear of an Italian invasion like it happened OTL. After all, having 400 thousand troops at your border defended by 40 to 80 thousand is concerning.
Ironically, Hitler's opinion of Mussolini might be more positive if he doesn't join the war. OTL he called Italy's DoW the worst DoW in history and hadn't thought the Duce to be so stupid.
Would there even be a Sea Lion plan in this instance? I would assume Hitler would not even pursue this option as consequence of a stronger British presence and if France fights on then it is even more likely he would stop all true preparations for said invasion. (So no air superiority needed -> no Battle of Britain)
- Hitler OTL already hated the idea of invading Britain and believed that any such operation could very well turn the war against Germany.
Now, the Soviet Union... while logistics don't really change, some of the opportunities lost or unused might. Germany in the case of no BoB or Crete invasion has a more sizeable air force and air transport force.
How could the forces used for the invasion of Crete be used against the Soviets? Perhaps they could finish some of the failed encirclements during the early stages of the war, perhaps secure Leningrad with the help of Bismarck (As with Raeder's more cautious policy in case of a more dangerous Royal Navy - he might keep the the Battleship in the Baltics until Tirpitz is fully operational hence could help during the push for Leningrad)
There's also the possible capture of Stalingrad if Rommel pulls another one like in France. OTL they could have captured the city with minimal fighting as for a few days it was badly defended, it was only thanks to a halt order (and traffic jam) that saved the city.
And lastly, the Japanese... would they even attack? In this TL they would go against a stronger Britain, possible French forces and US froces. They might have seen themselves in an overly optimistic manner but even then they realize the odds of winning against the US and forcing a peace.
I feel they might be too anxious of a war against 3 Great Powers, as, even if they win their decisive battle against the US navy, they will have to win 2 more against Britain and France, very unlikely to be possible. Japan might go 2 ways, go to war against Germany and grab the support of Britain against China or go to war against the Soviet Union and hope they could get their needed resources post Soviet defeat through the Siberian railway.