I'm at Day 11 post op on a 2300 FUE. Today, finally, I feel better at about a 2 / 10.
Just as you described, my pain kicked in on Day 4 and at Day 8 it was peaking. I have a high pain tolerance and this was likely the 2nd most painful thing I've encountered. I started to take pain killers on Day 7.
I think you're going to have to time when you take the pain killers. I started taking Aleve (lasts 12 hours) at 6pm so it would at least last me through the night. During the day, as painful as it was, I tried to ride it out - but when in dire need I took 2 Advils (lasts 4 hours).
The key thing is that it WILL get better. That's the biggest concern I had. It's my first HT and I was kicking myself for going through with the procedure to live with this type of pain for months.
I still feel some zaps in the donor area and definitely it's numb. Also, on certain donor wounds if I touch it brings the shooting pain back for a few seconds - so I'm avoiding that as much as possible.
Lastly, when pain gets ridiculously high I just took a nice warm shower and for me that worked wonders and relaxed the donor pain for some hours.