I just recently completed my first AG and had similar results and hopefully pinpointed my error to this as well (rushed sparge).It will still ferment fine, you'll just have low abv. My first ag was a little more than 10 points off. Found that I rushed my sparge runoff. Second time around I hit 83% just by slowing down the runoff. Could be your crush too.
Wish someone would have told me this my first time around. Worst case scenario, you wind up with more alcohol.When doing your first few AG's it doesn't hurt to add a couple extra pounds of base malt to make up for lower beginning efficiency. Then when you dial in your process you can back off a bit.