First dumb question: you know that the right hand BB thread is left handed?
Beyond that, PlusGas is way thinner than GT85. Give it a good dose every day for a week - if you can leave the frame so that it pools over the thread and has hours to seep in then so much the better.
Also heat shocking works well - a quick blast with a blowtorch is often enough to crack a bond. Of course you will be careful about the fire hazard of PlusGas and blowtorch.
After that, controlled force with the BB tool secured to the BB axle and a hooooooge lever (scaffolding pole works for me), and jobs a good un. But the emphasis is on controlled.