I had a similar problem with my first printer. Before trying a new hotbed or another PSU I just installed a very crude isolation layer below the heating PCB: a couple sheets of thick cardboard wrapped in aluminum foil. It worked like a charm and now that bed warms up much faster and reaches 120ºC+. Also, my results with ABS and hairspray were sort of hit and miss, with more misses than hits. Out of desperation, I tried UHU glue. That's also working very nicely.