Looks pretty rough, I assume the next step would be sanding it down. There is like a half inch gap between the board and the nose guard, I am thinking that instead of using dental floss, I will use an E guitar string and try to work it loose. If that doesn’t work, then I might try cutting the lip that causes the gap off the board ,circumcise it with a Dremel If you will.
Haha! if you can, please post a few pics of the surgery along the way!
I would start with a fresh razor blade to scrape what you can.
3m makes an adhesive remover liquid that softens and loosens most glues.
There is also a rubber adesive remover wheel that you can chuck in a drill and can buff stuck glue off.
One of these will probably work, the adhesive remover is great stuff but super exensive so I would try them in the above order to see if the cheap razor trick works first.