One item as I read back through the thread.
Mike is right in recommending 3M 5200. It's a go to in the boating market. Although there are some caveats to its use.
I was reminded of an experience within the past year when I watched, and minimally assisted a pro install a deck hatch and bulkhead on my P&H Virgo.
There was a good deal of conversation on which sealant/adhesive to use connecting the hatch rim. While we settled on 3M, research on their flagship marine products 5200 and 4200 indicated one key difference. If you may ever have to access/remove/work on the area again the 4200 stood out. 5200 is so good as an adhesive there is a real challenge if you ever have to break/remove this "permanent" bond.
Here's a brief summary of a comparison of the two products...
Finally, concluding the comparison between 3M 4200 vs. 5200 depends on the specific situation in which you will consider using either of these adhesives. You can go with the 5200 adhesives if you need long-time connectivity, more hardness, durability, and excellent joining for parts under or above the waterline.
But going with 4200 is also not bad as it provides faster curing with the latter dissembling of those joined parts.
The epoxy putty referenced in the video is also an able product for the repair you're tackling. Many use it for covering the sharp, dry bag destroying screw tips left exposed when installing a deck compass on both plastic and composite boats.
The best of luck with this.