Given that they're the little cube circuit breakers, they're not over 50A. I'd guess maybe 30 or 40, but that's just a guess. They should have markings on the metal can somewhere, but it's entirely possible they've faded or worn off over time.
Fatter cabling would be my suggested first change as well. Coachmen used something like 2 AWG on my class C, I haven't checked to be certain exactly what, with IIRC 175A fuses at either end. This wire (and the connecting solenoid) also serves for the emergency start system for use if the chassis battery is dead. I haven't tried to dust off the solenoid enough to see what it's labeled or rated for, but suffice to say it's still working fine for me. In normal use, the solenoid is not engaged when starting the engine, just with the run circuit (as for the radio and other switched accessories).
I'm not sure Ford information will be too much help here; it's not a Ford factory system but one the coach builder added, as I understand things. You can find the alternator rating at the least.
