And the ENY isn't just based on ATA ability, its also based on useage, and how much of an impact is has on the MA. Why else would the F4F-4 have a lower ENY than both the A6M2 and the 109E-4? The A6M2 doesn't see much use (and so doesn't have much impact) because there is a faster, better climbing variant with more 20mm ammunition using better cannons, swaping out one of the 7.6mm MG's with a 12.7mm, that can still turn just as well.
And yes, I can gain around 2500ft in the IID when going at around 250mph. For comparison, I've heard you can get around 6000ft in the P-38 doing 390.
And Ack-Ack, try shooting one shell at the town and then finishing it off with the .50's. It seems to be more efficent.