As far as the crack is concerned, I would take a look at it following the heavy rain. As Steve mentioned, these types of cracks are fairly common. If possible, look at the area in the basement during or after the rain to be sure no water is finding its way in. Assuming it does not, then you can likely leave the crack alone. If you notice that the crack does not get bigger or smaller throughout a couple of season changes, then you can patch it if you don't like the way it looks.
Regarding the hammering pipes, you likely had some air in the pipes that was causing the noise. This too is very common. It sounds like the air has found its way out of the system. You should be grateful! However, keep in mind, that it might return! If it ever gets unbearable, have a plumber take a look.