Just saw your post in my log. Didn’t want to overstep in my initial comment regarding ab work, but with your solicitation I’ll give you my perspective.
RE bench: I feel like you’re doing too much actual pressing in this correct workout and not enough assistance work. You’re doing 6 (what I assume to be) full ROM pressing movements in 1 week between 2 days, with minimal angle change (it’s either completely horizontal or completely vertical). For me, I’d fry out on that pretty quick (and I have done so in the past when I tried).
I would consider either eliminating the 8x3 bench on bench day, utilizing FSL if you want more volume, and spending some time on that day doing some tricep and bicep assistance work. You might also make the dumbbell work a push press rather than a strict press, in order to give your shoulder a slight break from pressing a dead weight so often. OR, instead, on OHP day you could switch out the 8x3 bench with some incline work, cut out the BTN press and make that a very much “bodybuilder” day with shoulders, triceps and biceps.
Also, on one of your upperbody days, I’d de-emphasize pull ups and put in some sort of row.
And, of course, my recommendation to chase everything with a set of band pull aparts. If that’s no viable, I like to do them at the end of the day before bed (100-200 reps).
RE Squat: I think your decision to train your abs is good. I’d also recommend doing some direct lower back training as well, to get the “whole core”. It made a huge difference in my life once I started training my lowerback. A reverse hyper is worth it’s weight in gold, but I realize most folks don’t have access to one. Do you have a normal hyperextension bench? That’s at least something. I’d probably remove one of the loaded carries and swap it out with direct lower back work.
On a personal note as well, I do much better doing my AMRAP sets at the very end of my workout, so that might be something to consider with the squat day for the FSL. Really allows you to give it your all.
I’ll give it a little more of a look over to see if there is anything I’d change otherwise.