Honest John,..... almost any good 100% acrylic paint will outlast any clear finish out there. So, there are no clears on this at all. The ONLY Time I use a clear, it is Clearstar, & that's only over airbrushed areas, because of how much you have to thin the paint.
Spar Varnish & exterior Urethanes usually fail within 2 or 3 years. I have signs all done in acrylic paints that are 13 or 14 years old that just now need to be re-painted.
For the record, 19 years ago, to ease people's fears about longevity, I raised my prices 10% & offered a "no time limit free first refurbishing" . Best move I've ever made. You soon find out what lasts & what doesn't, & which finishes are hellish to remove. I was using a lot of Sikkens Cetol at the time ........ it was the first finish to get the axe. Then 1-shot paint got the boot. Longevity is no longer an issue.
For the record, others warned me about having to do a maintenance coat on varnish & urethane every year, so I've never used it except for interior signage.
As for adhesive .... I use either Gorilla Glue or Dunabond. Both will "squeeze-out" but before it hardens, use some acetone on a cheap Q-tip to dissolve it. You have to watch it.