iPhone 6- Boot Loop- Error 9

My iPhone 6 (128gb) ran out of battery one night 3 weeks ago and because of lint, had a bad connection while charging. While trying to automatically boot up several hours later, it disconnected and ran out of battery charge. After more charging by morning, it came into a boot loop with the apple logo. Later that day, after messing around with resetting and charging, it got out of the boot loop (and I foolishly thought the problem was solved). The next day, it restarted suddenly but was able to boot up. A little bit later, it restarted and went back into the boot loop.

Not able to get out of the boot loop, I tried updating in recovery mode from 12.3.1 to 12.4.8. It crashed right as the progress bar appeared with error 9. I used the trial iMY Fone Fixxpo to get out of recovery mode and tried many different options to no avail (including cleaning out the lint). (I even paid for the pro version of Fixxpo but the update failed fails at 43% or gets stuck at 19%. Evidently, the pro version doesn’t seem to do anything iTunes can’t do. I think Fixxpo recognizes my iphone has having 12.4.8 even though iTunes barely even started the update for 12.4.8).

I really don’t want to lose my data that I haven’t backed up in a year and a half (last time I tried, it disconnected b/c of the lint and was too busy to fix and try again). Having seen others with error 9 not able to get it to restore successfully, even in DFU mode, I’m weary of trying to fix it by restoring in recovery or DFU mode and risk losing my data without even fixing it.

I’m using a genuine apple cable and I just was able to restore a friend’s iphone 6 on my computer with the cable and usb port with no problems. I’ve followed all of Apple’s troubleshooting and other’s suggestions except restoring or DFU mode (or opening the iPhone up).

Any suggestions? Any help would be much appreciated!! See this post for one of the error 9 logs. Sometimes it crashes as soon the progress bar shows, many times it crashes right before it would show.

Would using the iTunes version from the time of iOS12.3.1 help?
(cf. https://discussions.apple.com/thread/7253844)