Yep that's about right has you described it for battery life. Couple of things to consider in your future planning
- If you thought the battery was fully charged because you had the trailer plugged in at home using the converter, it might not be as charged as you thought depending on the converter. Could take days to fully a large battery
- Yes, for boondocking you need at least 2 batteries. The costco/Sams 6v batteries gives many of use excellant use and they cost about the same a marine gp24 battery. The 2 six volts will give you about 50% more usable power than 2 GP24 12 volts for about the same price
- Use a generator just like you plug your TT in to 115AC service. Plug it in and power up. If you don't need your AirCond then a 2kw generator will do it. If using AirCond you will need at least 3kw. Many of use the twin 2k honda setup (expensive but works great - quiet & low fuel use)