We have seen this once or twice before. Many of us are now careful when removing injectors to make sure we're always pulling with the force of the lever direct towards the inside of the head rather than the outside where the aluminum is very thin and can be cracked. I realize that info is not useful to you at this point though.
The only proper repairs would involve removal of the head. But given your situation I don't see why it wouldn't be worth an attempt to fix with TIG. There is no reason it shouldn't work and you don't really have anything to lose by trying. The only risk I think might be that it could make it impossible to remove that injector ever again. But that is a small price to pay if it gets the engine running again. Worst case if you ever had to get the injector out it would mean removing/replacing the whole head in the future.... but that's what you're facing right now anyway, so no difference to you.
If you try it, please share pictures and let us know how it turns out, we'll cross fingers for it to work for you.