to be honest i am not sure what is "correct" for sealing outside of seams, as i asked the same question and got mixed reviews but right or wrong i put a bead of 5200 under gunnels and along front bow seam before hitting it with paint i have attached a before and after photo.
Any reason you skipped the chine seam? What you did is just what I've been considering, only with the bow seams and chine seams, never even gave the gunnels a thought until now. I was picturing a smaller bead however, tape off the edges, lay the bead, smooth out with a finger(and lots of mineral spirits), remove tape, let cure, prime/paint.
Yeah, the epoxy will be a tough call. Daily temps outside are mid 50's to low 60's with drops into the 30's and 40's overnight, but probably much warmer in my attached, yet unheated garage. Thought if I could maybe keep the epoxy inside at room temperature, along with the transom until the first coat is applied, I might be okay with just a longer cure time. Sounds like the colder temps could compromise structural integrity/bond a bit, but not really sure what effect it would have on the "sealing" capabilities. I've already bonded the two 3/4" pieces together with Gorrilla Glue, just looking to keep out the water/moisture now.
I think you're on the right path with the sand and wheel on the interior...I was way overthinking it and got dazed and confused by all these bright shiny interior hulls on some of the previous resto threads.