More than likely the roof is TPO. You can clean it with regular cleaning products. I've scrubbed mine with spic n span. Just be careful, it's slippery with soap on it!
Just be careful with solvents such as mineral spirits and such. Those can damage the roof.
Yes, dicor self leveling to touch up around the seams.... just scrape/pull up any loose stuff. Clean it well then apply.
I think eternabond is probably a fine product and not overkill...but I personally wouldn't bother till it's time for a re caulk. Check eternabond's web site. they have tons of data sheets and videos about proper use and application. If it's put on wrong can imagine it could be a nightmare.
Oh, and my advice....don't use silicone caulk. In my experience it doesn't stick well enough to be a good sealant or a good adhesive....but it sticks well enough to be very hard to remove.... and once it's on, nothing else will stick to it.