This situation cries for further exploration. As Joe implies, you don't know the condition of your keelbolts, only that they are corroding and that there is enough space around them for oil (and seawater) to intrude. The exposure may be both from water in the bilge and from water coming up from the gap at the keel. I gather that you have access to the nuts.
I recommend that while you have her on the hard
you lower the keel a short distance, within the amount you can loosen the nuts without actually dropping the keel. Inspect it and dry it out. Then you are in a position to fill the gaps, both along the bolts and in the crack, with the water-excluding goo of your choice. You can take the nuts off one at a time to get better access.
Alternatively, and I hope that it is not this case, you will find that the bolts are seriously compromised. Still, better to find that out on the hard
rather than when your keel breaks off during a storm.
Good luck with it.