Where the gunwale has loosened from the canvas, I would remove loose paint, fair any chipped-away paint with spot putty (not the two-part Bondo used for repairing auto dents), sand smooth and paint. With any chips on the body of the hull (as shown in your third picture) I would sand/scrape to remove any adjacent loose paint, and the fair -- either by simply sanding smooth, or if necessary, using spot putty if the chipping can’t be faired smooth with just a little sanding. As this is not a place for water intrusion, nothing more should be required here, -- unless there is actual damage to the wood in the area.
The spaces between the keel and the hull, and at the joining point where the keel meets the outside stems are another matter. (I’m guessing from the first picture that your canoe has outside stems -- but maybe that’s just a joint in a two-piece keel?)
Is the canoe leaking along the keel? If not, you may get away with scraping out the old dried paint and joint compound at crack where the edge of the keel joins the hull, then using a good caulking compound to create a very small, smooth filet which should then be painted -- using an oil-based paint if you use a traditional oil-based caulking compound. I would clean out the joint between the edge of the keel and outside stems as best I could, and depending on the size of the crack, caulk and paint, or if the crack is too small, just paint, using spot putty to try to smooth the joint as much as possible. But because there may be old paint, compound, and dirt built up between the keel and hull, this may not prove to be a lasting repair.
If the canoe is leaking along the keel, just stuffing caulking or bedding compound into the crack is unlikely to solve the problem. Where there is even a small space between the hull and keel, there will be crud in the space that will keep the keel a tiny bit away from the hull, and as the hull flexes (as it will -- just a bit), the crack will reopen. The only way to get rid of the crud is to remove the keel and clean away all dried paint and joint/bedding compound and other dirt from both hull and keel, so you have two clean, smooth surfaces. Place a bedding compound like Dolphinite (perhaps after one coat of paint on the canvas) so that it will fill the space between hull and keel (and between the keel and outside stems) and will squeeze out as the keel is reinstalled. Remove the excess compound and paint, and you should be good to go for quite a while.
If there are cracks/spaces between the outside stems and the hull, I would deal with them in the same way as I would deal with the keel.
When I got my 1931 15’ Old Town canoe, there were minor cracks in the paint between the hull and keel, similar to those shown in your 1st and 2d pictures. For two seasons, I got away with just smoothing a bit of caulking into the cracks and painting. But subsequently small leaks developed, and for the next couple of years, caulking and painting did not eliminate the leaks -- just slowed them down a bit. The canoe is now being re-canvassed, and the keel (and outside stems) will be replaced, properly bedded, and I expect I will have no leaks for a long time.
Removing the keel from a canoe with outside stems is not usually done -- I’m not aware of anyone who has done it.
