S.B.
How important is this pot to you? I honestly feel that there is no way to get the entire residue out of the pot, and being that it is plastic, I personally would not like having an plastic in my food. I would feel that there might be melted plastic in future things I cook.
That's my only advice. I had a plastic grocery bag melt on the outside of a pot, and that wasn't a big issue for me, cos eventually I was able to scrub and scrape most of it off, but had it been a huge glob of plastic INSIDE, I would have just gotten myself another pot. Better safe than sorry!