Many people will try to connect their Rv to an external generator and not get the wiring connections correct.
It sounds like your generator's GFCI has told you that this is also your problem.
Because of this, you must check that you have the wiring to the Rv done precisely before you troubleshoot anything else.
I suspect that when you get these connections right, your RV's Air Conditioner will be Ok.
As to your Reverse battery fuse? I can only say that unless you have changed the wiring associated with the battery, then that fuse should have not blown from the other problem.
So, I would get everything in the Rv working properly while hooked up to Shore power and then get someone to check out your wiring to the generator.