See my posts here & here for some background material on learning to build custom iOS Scriv compile formats, using .scomp.
If it were me, I’d spend at maximum a couple of hours reviewing that material to see if .scomp might solve the problems. If it does, great. If it doesn’t, then I’d move on to @rms’ method of exporting to Word and formatting the novel there. (Spending too much time pursuing .scomp could turn out to be an unproductive rabbit hole.)
Best,
Jim