Breaking PR's, Pain, Shoes, & More

I am somewhat new to lifting/training, having started seriously training in March of this year, but I feel like I have definitely made some appreciable progress. I started out at 135 at 5’7", definitely skinny-fat, and within a couple months I was approaching 155 with not too much more fat, having made some really good strength gains. Then over the summer I attended a long-ass music festival (more than a month) and basically had to give up training, so I lost a lot of my gains.

I guess, if it’s relevent, here are my current stats at the big three:
Squat (Box Squat at the moment): 3x220
Bench: 3 x 175
DL: ~3x250 (Did 3x260 with a trap bar recently - it wasnt very hard on my legs but my grip gave out - I’ll have to get straps since I am a professional guitarist and can’t train my grip too hard)

At this point I have been lifting again since early September, and have now beat all my PR’s from those first few months, so I feel pretty good again, but there are still some things I have some ‘beginner’-type questions about.

FOr one, I have always had lower-back problems related to excessive curvature of the lower spine, seemingly caused by weakness in the abs, glutes, and hamstrings (a chiropracter told me this, and the articles I have read here seem to confirm it).

Currently, I am doing WSSBIII and really enjoying it - breaking PR’s is a ton of funand it allows me to explore more lifts than I might with a 5x5 or something of the sort. BUT I was wondering what the most beneficial lifts to getting my abs and glutes up to speed might be, worked into a program like this.

I’m doing reverse hypers on both leg days, and trying to really work hard on my weighted ab work, but I am wondering if maybe RDL’s or something of the sort might be more helpful to my upper glutes, which I am most worried about.

My second question relates to shoes.
I am currently lifting in low-top chucks, which I know is suboptimal. I am buying a new pair of shoes to lift in, and I am wondering if maybe Vans Sk8-Hi’s might be acceptable as an alternative to high Chucks. I have always loved Sk8-hi’s. They are flat, have good, grippy soles, and have ankle support in the same manner as Chucks, AND they are wide-enough for my crazy retard-feet (9EEE).

Any opinions?

(also, this post is super-long, should I just break it down into seperate posts for simplicity?)