@antinomy I have the same phone. Do you store a lot of videos on it? I thought the 64GB was filling up, until I found many GBs of podcast subscription downloads that I’d forgotten were there. Cleared them and freed up LOADS of space.
I plan to keep the phone for a few more years and will replace battery if need be. I’ve had glitchy charging and put it down to (in my experience):
1) charging port needs need lint cleaned out very regularly.
2) aftermarket cables often no good.