Tioga propane light blinks green, heater not functioning

Greetings from an Autozone parking lot. I’m Harvey and I bought a nineteen foot 1998 Ford Tioga in pristine condition two weeks ago. In order to best explain the problem in full, I’ll need to start at the beginning. A day after I bought the vehicle the carbon monoxide detector started to intermittently beep occasionally in about 30 second intervals. I noticed it periodically during the week I spent planning for my big adventure, occasionally stepping in the vehicle and hearing the sound. When it was finally time to hit the road I went to turn on some lights but they would not go on. The short story with that is that the two Interstate GC2 house batteries had drained completely and could not even be resuscitated. So then I went out and bought two Interstate deep cycle GC2-ECL-UTL 6 volt batteries (an upgrade) on my way to my first state park. I turned the propane on via the Pre-Tell 2 LP Gas Detector, eventually noticing that, unlike before, the green light did not stop flashing, did not turn a solid green. But the lights now worked, and the stove worked, so I figured everything was OK. Cut to 2 days into my trip into the cold desert, and I gradually found that the heater would basically not work - it would blow cold/normal air, or occasionally blow hot air for a very short while, then turn cold. Also, the fridge/freezer seems to have a mind of its own, getting cold quickly or very slowly or not at all. Additionally the bathroom light stopped working altogether. Eventually I googled the issue of the flashing green light and… It signifies something to do with… the current/ flow/electricity not being properly conducted. I had the batteries tested and the AutoZone man says they’re in perfect health, along with the hood battery. Meanwhile, all the electrical functions in this RV worked fine until the old batteries died and were replaced - so are somehow these deep cycle batteries the wrong fit for this rig?? Incidentally, regarding the carbon monoxide alarm, I’ve had to wonder whether it was actually broken or was just responding to a dying battery (it lights up green, but I’ve actually tested it using the tester button, and it doesn’t work - but it’s no longer broken in the sense of intermittently beeping). I am providing all of this information because basically I can’t figure out why the green light doesn’t stop flashing, and I associate the flashing with all the mentioned problems I’m having with the appliances. Because apparently the propane is not getting the proper signal/electricity/current/flow. Although I am also confused with how the heater actually works - I thought it ran on propane, but even when I turn the propane off, when I turn the heater on via the Coleman Mach controls, the air still turns on (although almost never hot, as mentioned).

So, I need help in solving the flashing green light issue. I’ve cleaned and tightened the various terminals associated with the house battery, and also removed and reinserted certain fuses, checked the hood battery (it’s fine) but no luck. Mr. Goodly AutoZone Man also took a good long look, but couldn’t uncover the issue. He recommended I get on this forum so here I am. Any help would be much appreciated.