Agree with Jeff
I would also HIGHLY suggest re-installing the speaker as well before installing the battery - it was a very tight squeeze as the bottom-right of the battery was snug against the speaker when I tried to get that back in.
I ended up going to a jewelry store, and they drilled down into the screw, with of course an incredibly tiny bit. That allowed me to insert the P2 driver, and I was able to unscrew it at that point. Good luck!
One of the pentalobe screws is stripped :( - suggestions for how to get it out?