I have 2 8535s which should be pretty close to yours.
If I had your problem, here is where I would start.
Not clear from that page (IMHO) under "Sooting" are a couple of items:
1. A blockage in the the heating chamber could be from mud dauber wasps. To see that you are going to have to remove the gas valve which means turning off the gas to the RV and purging the gas lines before breaking the connection to the valve.
2. Problems with the gas jet itself. It is simply a small orfice that could be partially blocked. Don't use any sort of wire to try to clean it out.
You should be able to quickly tell if you have good fan speed, just by listening and my placing your hand near (not directly in) the exhaust air flow. Lighting several burners on the stove at the same time should also quickly verify proper gas flow, though checking with the manometer is much more accurate.
The low voltage mentioned would likely come from the house batteries and will affect the fan speed.