First of all, welcome to the insane asylum!
If you're planning to run a CPAP machine off of house batteries, make sure you set up your battery bank to have plenty of amp hours to ensure it will run all night without killing them. I'm not sure what the power draw is on those but double and triple check your total draw for your essential hardware, then I'd say go at least 1.5x that number. Only reason I don't advise higher is since you said you had a backup charging plan (coach engine) to the solar array. If it weren't for the CPAP it wouldn't be as big of a deal but you don't want to do anything to risk your health so better to go too large than too small.
There are a couple of currently active threads on composting toilets, might want to read through those too.
Sounds like you've thought out your initial phase fairly well.... before fastening anything down though, set everything up like you have it designed if you have everything, otherwise use tape/cardboard mockups, folding tables, etc to simulate it, and live in it for a week or so in your driveway or yard, or in a nearby campground if no other option.... it's easier to move tape and cardboard, or otherwise shuffle things around than it is to have to unbolt everything, move it, and drill new holes and reinstall. The plan that looks good on paper frequently doesn't quite work out in practice... once you have a workable solution that works well, then you can fasten it all down.
Any other questions, there's plenty of threads here that should answer them, and if not just ask, I'm sure someone will know, or know where to find, the answer.
I'm sure others will chime in with their own suggestions/encouragement.
And one more thing, we're a very visual group so we want to see pictures, and plenty of them!