all the baths you have given dollar has probably washed away all the frontline
if the white dog had bad fleas its fur would not be white but a manky brown white
just curious do your floorboards have holes in them? the fleas could be living under the boards and hoping out through the cracks/holes
if fleas are biting you then there are still fleas about .. tell that to your new vet and beg for a solution to sort the problem
psst move house.. start a fresh in a flea free home