Regarding Italy:
- If the allies make clear their 'suspicios' and 'dislike' of Italy continued commerce with Germany Mussolini answer (before the translation in diplomatic speak ) will be: stuff it, we surely won't starve or freeze for your pretty face.
In this moment Germany is one of our biggest commercial patners, and more is our biggest supplier of coal, so if now Italy had more 'strenght' in her economic relation with the nazi, suddenly cut out or even greatly reduce that tie will cause severe damage to the italian economy so it will be a gradual thing...unless the allies (or better the UK) decide to step in and offer to supply her Italy (better if it a good deal.)
In OTL a similar offer was done, but at the same time of the menace of bombard rail and ships who were transporting the german coal to Italy...so no, Benny really doesn't like that proposal.
- Speaking of colony, well sure Ethiopia will be always violent and a resistance movement exist even at the moment. Unfortunely even if the war created a surplus of weapon, the big problem (not only in this situation, but worldwide...and this will affect any immediate postwar liberation movement) is the fact that is very zone specific. Unlike OTL, Africa (and south Asia) is quiet and there will be no left over to arm any rebels, and even if the Soviet want supply the Ethiopians, there are lot of logistic problem, the coast that are not in italian hand are under French and British control so i doubt that they will gladly help the rebels, plus in the italian controlled coastline the local population really don't like the ethiopians (who were likely to fight each others as the italians)...to put it mildly. The rest is desert actually controlled by others colonial powers so any supply route will be difficult to mantain.
Lybia will be pacific for at least another generation...due to the previous italian anti-insurgent campaign (aka massacre anyone that even think to resist) and during that time the number of italian colonist will increase greatly even due to the discovery of oil, so by the 60's the native will be a minority in their land and a similar situation (great numbers of colonist) will be repeated in East Africa muddling even more the situation.
- conceive the exact number of nuclear weapons from the Soviet is difficult but not impossible, expecially in the 50's and 60's...at least directly.
Air reconissance at long range was never the strenght of the soviets and any communist agent or anyone really, found near the lab, nuclear central and deposit will not fare well.
Indirectely is possible, soviet can penetrate the French and British intelligence ...and they are good in send aircraft over the possible italian nuclear site and from that data they can extrapolate the possible numbers.
- Italian will declare war...at least when the writing will be on the wall, on that anyone can be his reproductive organ.
Benny will surely want be part of any diplomatic conference about the post-war new order, plus for Mussolini Austria need to return on the italian sphere of influence or at least become as OTL Finland and surely any communist thrust need to be blocked.
- on the italian forces on Romania, honestly i know that from a narrative pow there is the need to keep Italy occupied; still a force on par of the Armir will not be kept unless there is a war due to the cost (for both Italy and Romania) and the need of the men for harvest and industry and even the URSS can cheaply keep almost a million of men mobilizated indefinetly if there is no war. In the end, the bulk of the troops will come home, something akin to the italian expeditionary force in Spain will remain in place, a formal alliance will be signed (even with Hungary) so in case of another crisis Stalin will know that there will be a strong military resistance and reinforcements will be on the way, some agreement with Yugoslavia for the passage of troops in case of the mentioned crisis, maybe some 'request' to Franco for send some troops to help against the communist aggression and protect the Balkans.
- as i said relations with Italy will be complicated, first even if there is a sizeble presence of italian troops on the Balkans this doesn't mean that others cannot be raised (even with difficulty regarding equip them...but less than OTL) and the troops are in Romania so Mussolini can take (at least theoretically) the decision to bring them all back home if he feel that is more important so or the Wallies (or anyone for the matter) are too menacing.
The Anglo-French on their side are not losing the war, not winning, the end seem (on their perception) distant and there is the need of lot of preparation, expecially if they want minimize the loss both human and material on their side.
Not counting that with Japan seem to want to start trouble in Asia, the war (and the relative cost) will expand...so keep Italy happy will be paramount for the Wallies diplomacy, expecially if they are seen as an help to contain the Soviets (that honestly from ITTL pow can be considered an hair short to be effective and co-belligerant german allies). Not counting that if the postwar see an URSS on the expansionist route, bring Italy on a renewed Stresa front will be seen as paramount; sure after the invasion of Abyssinia the relations between the powers deteriorated but never on the breaking point and the Wallies till before the OTL fall of France worked to patch things up (ITTL both London and Paris are really unware on Benny intentions of enter the war on German side as frankly there were no italian preparations regarding that...and the only official document see as the italian goverment tried to stall things when Berlin asked them to attack France.)
So even if they are not BFF, between the three powers things are not so bad and in the postwar situation seem that they will need each others (even regarding decolonization)