ya know StoneRidge it is odd that your above thread did not get any response. I know for fact that most of those subjects and questions have been addressed on these forums before. If I can find some of the links I will post them here for others. I know from further reading your reports that you have long since passed the point of needing this thread answered.
I recall that Overlander 64 had a thread long ago about the refinish of his bathroom/s. He is one of the forums best reporters. However I recall he had his work out-sourced. (He hired it done.)
There have been at least several other detailed reports of DIY bath refinishing.
The ceiling sections are "officialy" known as "domes" and I believe are made of fiberglass. The bath panels and fixtures are made of ABS plastic. Apparently there are dozens of forms (formulas) of ABS plastic. I know there are threads here about "plastic welding" which deal with attempts at fixing the damned stuff.
As for caulking there is a long thread on that subject, but it focuses mainly and perhaps exclusively on exterior caulks & sealers IIRC (if I recall correctly). Interior wise I would think that the dreaded Silicone could be used on non metal applications, but wouldn't the deluxe (improved) tub-&-tile caulk make the most sense? Not sure how many colors it comes in, nor whether it could be colored (then how would you get it back in the tube?
Again I know you have long since moved on with the AS-rehab but I post here mainly to keep this important thread from being a dead stub.