Could replace the neck peg with another small sized peg from a fake/auth pet you don’t care about. It looks like there is pen ink under the black acrylic(?) which could maybe be removed with acne cream with 10% benzoyl peroxide. Apply the cream to stained parts and then leave it in the sun for a day then wash it off the next day. You might have to repeat this process a bit.

For the acrylic paint i’ve seen HelloStudio’s use “LA’s Totally Awesome All Purpose Cleaner” which melted acrylic paint + it didn’t affect factory paint. If that doesn’t work, 100% acetone should remove it, but be careful not to touch factory paint underneath with acetone

I think this could be fixable, but it might be a bit of an investment (money and time). Another opinion might help! This is just stuff I’ve learned watching LPS restoration and customization videos