Sorry to hear that! Where was this, out of curiosity? Did you get hit by the big storm in Corsica this August?
It's a tricky one. I'd say the damage at the front is too significant to just fill with caulking and ignore. There's a gap now, so something has deformed permanently. It may be the frontmost bolt has broken or stretched or the hull has deformed. There's a certain plastic deformation the GRP can have without delaminating, but it would need to be inspected thoroughly. Beginnings of the stringers detaching will not be visible in the bilges, but it will be if you stick an inspection camera inside the limber holes and look from _inside_ the hollow stringers. Bit tricky, but possible.
Since the insurance is paying and for both peace of mind and considering a sale at some point in the future (even if you're not planning to now), I'd get the keel dropped. The fact that the yard warned you about further damage tells me they're not entirely ignorant of the job at least, a very good sign!
The keel is glued on with two-part methacrylate glue, which is as strong as epoxy and will pull off laminate if forced apart. It's meant to make the keel a permanent part of the boat on installation.
So I'd see to cutting it as much as possible. Starting at the convenient gap at the front, using an oscillating multitool with saw blade. Don't worry about damaging the bolts, they probably should be replaced anyways after this experience. After you worked your way around that as far as possible, a hacksaw blade should do the rest. The job is probably best done with the weight of the boat off the keel, so it can gently be lowered as you cut. I believe the mast must also be removed first as a sailboat without keel is not stable in a boatyard cradle with the rig up.
The keel weighs a couple tons, so the only tool you need to remove it is a strong support for it, ideally with wheels or forklift access and the travelift. Else the boat must be hauled away from the keel instead. Type "keel removal cradle" into Google image search and you'll see some examples. Once keel and hull are supported separately, the bolts can be undone inside the boat. When the boat is lifted off the keel gently (see above - while cutting, not tearing!), the keel will simply stay behind, hopefully not taking any of the laminate with it.
The rest is a thorough inspection, cleanup of the mating surfaces, possible repair of any damage inside and out and then re-attaching the keel - making sure it's on straight!
Take plenty of photos for insurance and to reassure future buyers that the job was done properly.
The keel is then reinstalled (instruction PDF in the Download section here). The gap is faired with the squeezeout of the glue and finally sanded, primed and antifouled.
Good luck!
