Definitely you need a new AC. Should not be a problem. We had a mobile RV service do ours but you could drop it in yourself if inclined. I am not a fan of the on demand WH. I like gas WH for a trailer with 30 amp service. I would put in a 6 gallon Atwood gas-electric WH and run it on gas. Power is already limited when the AC is running. For the same reason I would get a gas stove too. For me probably a 110 fridge or one of the
12 volt marine fridges. My reasoning is that power is limited and that gas is more efficient for heating water and cooking. And propane refrigerators are not near as good as compressor driven ones. We winter in FL. I use one bottle of gas a month for heating, WH, and cooking. Not a big expense and cheaper than when we used the electric heat and water heater.