This is hilarious, a truly ridiculous story. First we need more details on this broken back squirrel story. Some brush on superglue would be probably the best sealer you could use on the bones. They make a really runny form that comes in a bottle with a brush for applying it.
I can't wait to see some actual bones in an aquascape. If done well, it could be really cool. I don't think an articulated squirrel skeleton will look good though. You can only do something really un-natural and cheesy with it, like have it clinging to some driftwood. To make a natural scape that had a squirrel skeleton, basically you'd have a pile of disarticulated bones, half buried in the substrate. Meh