I need some advice on how to remove the remainder of an old gasket from an oil pan.

As you can see in the photo; I've already removed about 70% of it and I now just need to get that big thick chunk at the widest part of the rim. I have used all kinds of scraping tools but I believe I am damaging the rim of the pan.
I think I might have already damaged the pan when I attempted to sand of a stubborn corner on the other end (see pic below). I won't know until I get the new gasket on and bolt it back on to the bike.

If by some miracle my sanding hasn't destroyed the pan; I would like to try and remove the remainder of the gasket without making it worse.
Any ideas would be much appreciated.
Thanks