#1 I would look at why there would be metal fatigue? If the bridle is pulling at some new angle other than what it was designed for, then that would have to be addressed. If you want to fix this right you will have to cut some holes in the hull. I like to use a rotary grinder/sander with a 6" wheel you put 36 grit paper on it and grind a hole under and around the broken tang for about 4 to 6 inches below it. That gives you enough room to work and maybe get the broken off tang out of the hull. It also gives you a feathered edge from which to re build the hull. If you can find a fiber optic device and fish that into the hull under the tang, that might help to diagnose the fix too, and see what the best plan would be where to go in, etc.

If you haven't done much fiberglass work yourself you might want to get a book on the subject from the library. One good one is "The Gougeon Brothers on boat construction" or "Fiberglass Boat Repair & Maintenence" also from Gougeon brothers /West System epoxy.

It's no fun, but it's possible.