I think the bigger question is when should Sea Lion be aborted?
Should one abort all plans for Sea Lion if, say, Italy is diced hard in the Med and lost the majority of its transports/fleet?
Probably, because one would assume that the main goal of Sea Lion is to stop the Brits in Africa so that Italy can rapid expand. In this case, Germany is better off going after Russia. The argument can be made that one is, at the very least, gaining the British IPCs, but in reality one has gained nothing since one will not even be able to re-build the airforce and, thus, leaving one to struggle on the eastern front and unable to repel the coming American wave.
If the Germans take too long to assemble the units required for a sure thing Sea Lion, it should also be aborted. As mentioned above, by this time, the US, in theory, will be too potent.
What if Germany lost an abnormal amount of planes during T1 or T2?
Sea Lion should most definitely be aborted.
As a UK player, one should also note all of the above because these are all tells as to Germany’s capabilities. If, for example, Germany lost a lot of aircraft in T1, one should conclude that there is a Sea Lion reprieve and can focus on Africa.
In sum, if one is playing as the Axis and is wielding a weak, transport-less/fleet-less Italy, then what would be the point of Sea Lion?