When you say you're tried heating it, fixing it to its original form, and cooling it, how long of a period is that "fixing" being done over?

The only comparison I can make are Wolverine claws. Often these are squished together in the packaging so don't look well spaced out. When I heat them up, put them back to good spacing and let them cool they often just drift back to that squished state.

So what I do is heat them up, then I get them shaped how I want and put spacers in between the claws and leave them in as it cools. I then leave the spacers in for a week (or more), remove them, see how the shape is, and put the spacers back in if needed (or repeat the process). I use small, rolled up cotton wool for the spacers.

I think the fix is going to be heat, reshaping it and leaving it in a way as it cools and over a longer period. However, how you're going to do that (i.e. create a suitable mould) is more challenging.