You cannot do this without completely destroying the boat.

Your best course of action is not to repair, but to replace. A "crack" big enough to cause the hull to sink is a fatal structural failure - in a place where the boat doesn't usually fail.

I'm guessing that the boat has wings. If you want to reinforce the hulls at the crossbars, you do it via deck ports - two are already there.

Has it occurred to you that sailing an old boat in the open Gulf of Mexico - alone - may not have been the smartest thing to do? Were you prepared to be out there for several days? What if your radio hadn't worked?

You're lucky that it wasn't the USCG that responded. They would have taken you off the boat, back to the CG station (Key West) AND you would still be responsible for recovering the boat.