Due to the charging requirements of the bike to pull the heavy trailer, I think that your current plan has a very low likelihood of success.
Have you considered that your camping opportunities may be limited due to limited mobility and visibility of the trailer? You are not going to be able to be very stealthy.
Based on what you have shared, may I suggest that you either back-off the heavy trailer option and go with a tent, or go with a motorcycle and trailer? The $1500 you are going to spend on the E-bike kit and the money for the solar panels will buy a decent motorcycle. A good mid-mount E-bike kit will cost that much or more once you option it out. Or the money would go a long way toward a good tent and gear, and living expenses on the road.
Living here in SoCal, I have met many people living out of a tent on a bicycle while camping at the hiker/biker sites. There are also many folks living off a motorcycle (see some on YouTube).