Jandjbaums, solar is always "too much information". When big guns here fire up, I sometimes don't know what they are talking about. But then maybe they don't know either ;)
45W kit from HF is an overpriced battery maintenance kit, meant to prevent the battery from self-discharging when it's already full and all the loads are Off. It will collect 10 or 15 AH a day at best. Too little to run any loads, and too much to compensate for self-discharge - 5W panel would do that. On a good day 45W will barely supply what you LP fridge is drawing over 24 hours.
Start a separate thread on 120V battery charger. This has nothing to do with solar. IMO, a converter in your trailer already a 120V "charger", though you might want to upgrade to a better model.