Sun Cat and keel bottom sealant

[RubberDuck]

I have a Sun Cat that I got new from Com-Pac last year. At some point I have managed to scrape the side of the keel on the trailer bunk. I thought it was fiberglass and was prepared to patch the scratches with epoxy. But when I inspected the keel, I realized the damaged area is on the rubbery-feeling caulking around the bottom of the keel. I think it might be the 3M 4200 sealant or similar, but I'm not sure. I attached the diagram.

So I scraped off parts of the sealant that were damaged or detached from the keel. I plan to re-seal the affected ares with some 3M 4200.

Questions:

1) Am I right that this seam is not structural? That is, can I use a flexible sealant like the one I think is already there?

2) Is 3M 4200 a good sealant for this task? I obviously can't ask Com-Pac any more, and my dealer has been surprisingly unhelpful so far.

2) Can I keep the old sealant where it hadn't been damaged? Is it okay to only remove the bad parts and re-seal there? Will the seal be weak in places where the old sealant meets the new one?

Here's a 3 minute video showing the problem: