Re: how to salvage acrylic painting on wood panel...
my recommendation would be to sand it down well and give it a good couple coats of a true solvent-based primer. This is a pigmented resin that you can cover practically anything with it, and paint anything on top of it (water or oil based). A good paint shop can even blend a custom colour, so you don't have to work with just white, grey or black.
"Never ascribe to malice what adequately can be explained as stupidity"-- Robert J. Hanlon
“What a genius, that Picasso. It is a pity he doesn't paint.” - Marc Chagall