Oh! I'm so sorry...
*hugs*
he was already late and behind the others. sometimes there are complications we can't understand, like the positioning you mentioned, or something else. if you do an eggtopsy, it should let you see how much fluid was still in there, and how much yolk was absorbed, etc. I understand if you don't want to take the egg apart, but I do encourage it because it helps when you're "picturing" what's happening inside the egg during your next hatch.
do not feel guilty at all, your accidentally pipping him had nothing to do with this. I have pipped eggs that have lived many times and was prepared to take you through the steps, though it is not commonly done. if you are finding blood in the membrane, then you are right to stop and wait longer. you did absolutely everything right. sometimes, they are just not strong enough to hatch for whatever reason... genetic, nutritional, conditions, it could be anything.
and great job on the chick you assisted earlier! this has been a great first hatch, that's an amazing hatch rate that you should be VERY proud of everything you've done! you have a great attitude toward hatching, and I bet you know a lot more now for your next hatch (and there will be many hatches to come, this stuff is addicting!)