I will try to answer your questions as well as I can.
1. The floor is made with a composition type board and is very solid, I don't know what its technical name is, structure wood, etc. I have never heard of any rotting.
2. Formaldehyde out-gassing? Can't answer that one, but I guess there could be some as there are many commonly used materials in the units.
3. 110 volt DSI water heater means that it lights on propane with a 12 volt Direct Spark Ignition, no pilot light to light. It also has a 110 volt heating element that can heat the water when you are plugged into shore power. You can use them both together for a faster water heat-up. This is all controlled by two switches inside the trailer.
4. The drop down bunk has at least a 230 pound capacity, I believe.
5. The solar charger is meant to be a supplemental charger that will supply a charge to the batteries to extend the life while away from shore power and to keep the batteries at full charge when the trailer is not in use. It will not supply all the power needed to operate the electrical needs of the trailer by itself. I don't have that option.