I think you were concerned about nothing. There is no strength in the gelcoat. I would stop where you are now. Now, I would first free the keel hangers and give them a light coat of grease. Also apply some grease to the weldment threads and the hanger bolts. I use WEST epoxy products exclusively for many years, and highly recommend it. Next, I would make sure the area is properly prepped and clean with acetone. I use disposable acid brushes, but I would mix up some WEST epoxy and give a light coat to the area. Now mix in some thickener, I would use 404 High Strength filler. Mix to about peanut butter consistency and apply in the area, one side at a time. Now install the hangers, bolts only snug. We're going to use the hangers as the mold. The grease will prevent the epoxy from sticking to the hangers, weldments, or bolts. Do the other side the same way. Let it cure overnight, and disassemble. Clean up any drips and finish reinstalling the keel.
Hope that helps,
Don