Thanks for all this constructive actionable feedback and encouragement!
If my form is improving it's definitely thanks to you guys' feedback here on the forum.
Slow down. That's an enticing idea. I will try that next.
I do feel rushed and stressed during the squat working sets. It feels like a game of whack-a-mole that I can't keep up with. Ass to the wall! knees out! face down! lead with the hips! I'm lucky if I manage to do even one of those things in the heat of the moment. I thought that the stress was due to the heavy load but I can believe it's partly due to haste.
(I especially felt this on the third set because my neighbour in the next rack commented that I looked dangerously bent over forward on the second set. I couldn't quite work out if he was giving me valuable safety advice or mixing up techniques e.g. thinking I was doing a high bar squat. It made me self-conscious and exacerbated my "yapping dogs in the brain" problem on the last set.)
The notes about injury risks are appreciated. I will try to especially take more care to rack the bar slowly and safely.
I have ordered a belt. Leather, 4" wide, 10mm thick, untapered "powerlifitng" style, reputable brand. I understand that this will probably be better suited for squats than deadlifts. I look forward to learning how to use it and treating it as one more tool in the toolbox.
The dumbbell grip article is a revelation. I am amazed that grip can be the root cause of so much of my problems. I will practice the alternating and hook grips for the working sets and last warmup set.
Also on grip: I'm not allowed to use powder at this local commercial gym where I have been training. Maybe it's time to shift focus to the other gym I have access to which belongs to the local "power sports" club.
Speaking of the power sports club I'm planning to sign up for a friendly competition there this Sunday. I'm told it's mostly a beginner-friendly social event where people lift a weight they are comfortable with and track their progression from year to year. The people there seem very friendly and experienced. I'll bet they could help me find the groove on my bench press quickly.
I might miss one workout this week in order to stay fresh for Sunday and play a two hour basketball game on Friday. Maybe I'll be tempted to squeeze one in on Saturday though. The basketball is a bit of a conflict but there are only two games left before the summer break and then my only sport will be strength training for a couple of months or so.