Cracks at the keel/hull joint are not uncommen, but you should clean it out and refair it. What is a little confusing is you say the crack is forward of the keel. Is the joint you refer to the hull/keel joint or something else.
The flooding bilge would concern me. Do you have an auto bilge pump
? If so, new batteries may mean that the pump
is able to keep up with a leak, and stopping water from collecting in the bilge. I am not sure any other connection new batteries could possibly have to water in the bilge. At any rate, you should determine for sure whether or not you are taking in water. If you are you do need to determine how it is getting in.l
Where does the head sink drain to? If it drains into the bilge, whatever is in the bilge could certainly back up into the drain.
If I were you, I think I would have a surveyor or your boat yard look at the keel. They are bolted on and can come lose. it is unlikely it would just fall off suddenly, but loose bolts could definately cause leaks.