Hi, I saw that a mod on a forum replied to you about the damage comparison between ABKM and Gotland. If I were to use the formula and bonuses here, you'll find some discrepancies.
I'll make a quick work to focus on anti-installation damages. So, I'll assume that the numbers from the guns' firepower and improvement are correct. Thus, ABKM has 82 firepower, whereas Gotland has 88.
Firstly, it's a major error to assume that the anti-installation bonuses will be post-cap. Always assume that they're pre-cap because the only enemy with notable post-cap bonuses alongside pre-cap ones is Supply Depot.
Secondly, additive bonuses are applied AFTER multiplicative bonuses. You can look for that formula in the link above.
So, you will have something like this when DA-ing Central and Airfield at night on E-4: