The glue is a real pain and sounds like it has leeched into the timber.
My only suggestion would be to continue using whatever dissolves it with a rag or many... you'll suck a lot of it out. Then let it dry completely.. it should NOT be tacky to the touch then. Id leave it for a good week to fully degas itself.. if you dont so this, your seal will lift in parts due to the gassing underneath. Vinyl glue can normally be removed using meths... its what we use in the sign trade... or White Spirit
Then seal it with the cabbotts as you have described.
Im guessing here.... but this is what i would do in the same position
