"I pride myself on mental toughness so it’s not simply a matter of being lazy or cowardice." What? What does what you take pride in have to do with your performance? You could just be wrong. Your post gives the very strong impression of someone who's dramatically over thinking their training. If you're 40 and have been lifting for 10 months you probably literally don't know how hard you can push yourself, you haven't trained long enough or hard enough to have that experience.
Why worry about minutiae like optimal weekly set range for hypertrophy or your mesolimbic neurotransmitters when you're a novice lifter? You aren't eating in a calorie range for optimal hypertrophy no matter what set range you are at. By your own report what you're doing is working so just keep it simple. Don't go looking for problems you don't have.