If you developed the crack after heat treating, you may be able to salvage it. I just did it, myself. Just this week, I made a little bow and I had undulation dips in each limb at near mid-limb. They were sister billet splices. It followed the string about an inch when it was done, but appeared to hinge at the dips. Again, appeared to, just may have been the dips. Nevertheless, I heated the dip areas and thought maybe I could bend them backwards a bit. Like you, I cracked the belly side. Pushed them a bit too far, I guess. Anyways in each case, I left the limb on the form, keeping the crack open and put CA gel glue in the cracks. Since the cracks were on the compression side, I thought it would work.
It worked. The cracks sealed up and the bow now has about an inch of reflex. It also gained about 3 pounds in draw weight. I shot several arrows through it and is holding up well. I'd show the rest of the bow, but I just dipped it in my finish an hour ago and I'm certain it is still tacky. The entire bow has trouble spots that I fixed. It was one of those pieces that I wasn't gonna let beat me.