Isolator issues

[Sunbear]

paid someone to install an isolator in my bus? Cause I have a breathing machine I need to use every night in order to survive. Now my bus is broke down homeboy got paid and skidaddled to oregon. So far ive figured out that I have a 140 amp altenator and he installed a 95 amp maximum isolator . the inside battery bank consists of 4 6v golfcart batteries my starting battery is.a.12 v d cell big ass monster. I cant tell if the auxiliary batteries are.charging because they have only had cellphones charged on them , the starting battery on the other hand after being drained when I drove for 15 minutes from having my lights on took a charge and stayed charged until I drove the bus again a week later the alternator doesn't smell burned up at the volt meter said it's putting out 11.4 amps which is not enough or maybe thats volts yes volts . Soooo my question is does anyone think I have damaged my alternator but having this too small of an isolator hooked up although there is a breaker between the battery and the isolator
I TOOK my 12 v d cell to the parts store they said it would not take a charge so I bought a brand new one now my bank of 6 v batteries doesnt have enough power to run the inverter but the old 12 volt still does