Idk the kind of lizard you have but i do know some lizards can regrow their tail if its cut off and it tends to not be much of a hinderance because of that (its said it can regrow like 6 or so times but again lizard dependent i think)
As for the arm that wont but i wish you lizard very well, you from what ive seen on here have been an astonishing lizard owner and love that little thing with your heart and soul
This is not your fault
Think of the positives even in the worst of downward spirals
It’s going to be okay ❤️