At this point you might be out of luck and have to dig out into the next joist bay and replace from there over. You cannot chip out PVC from a hub. If you're in that situation again, the best thing to do is cut the pipe off flush with the end of the fitting, then go buy one of these... http://www.plumbingsupply.com/pvcsaver.html for the size you need to drill out.
Problem is, if you don't do a lot of plumbing, those tools aren't worth the cost, so you just end up cutting it out and redoing it anyway.
I think, had you not cracked the top hub, that there are also flanges made that can be solvent welded to the outside of the hub fitting, but not sure about that one. Now that its cracked, you pretty much are best off just cutting out those fittings and putting in a few new pieces.