Hey! I'm also a 41 y/o career change pilot. Congrats on not just talking about it but DOING IT! Got my Commercial Single in January, have my CFI checkride on Tuesday.
I LOVE Power-Off 180s. Currently on an unbroken streak of 19 successful PO180s in a row. To get to this comfort level, I did the same sort of thing you're doing, practicing the maneuver in lots of different conditions. Here's my tips on locking it down. Disclaimer: advice is based on Cessna 172 aircraft.
1. Setup the same way every time. Same airspeed, same altitude, same distance/sight picture from the runway on downwind. Once you're abeam of the landing point, pull carb heat & power and pop a notch of flaps (10 degrees). Turn base the moment your airspeed matches best glide speed (should take 3-4 seconds) and trim accordingly for ease of control. From base you can correctly gauge if you need to dog-leg it directly to the runway or box it out to lose more altitude (remember to take wind into account by looking at the windsock on downwind EVERY TIME).
2. Specifically practice coming in too high and coming in too low on final. This way when you make the wrong call on the base leg, you've still got options on final approach to salvage your landing.
Too High: Flaps to 30 degrees, put the plane into a slip and drop altitude like a pro. Once you're out of the slip, feel free to drop in those extra flaps (don't slip in full flaps configuration, it's a bad habit). When you're approaching the target landing spot, don't be afraid to put her down hard. Just make sure you're not coming in with excess speed, use the slip to bleed off altitude and keep your speed in check, ride the slip all the way down if you have too, DON'T try to land at high airspeed. You'll bounce, nosewheel-barrow, prop strike or porpoise (in other words, you'll fail).
Too Low: I can explain this to you all day but you won't get it until you TRY IT. You're on final, you have 10 degrees of flaps in and you're coming in too low/too slow. As long as the approach area is clear of obstacles, push the nose down and increase your airspeed from 70 mph to 80-85 mph. Yes, I know your aiming spot is now grass, that's okay. HOLD THIS. You're going to round out once you're in ground effect (yeah, LOW). Don't flare. Go to full flaps once you're in ground effect. The extra airspeed plus the additional lift being created by your flaps in ground effect is going to float you down the runway. Slowly increase back pressure to stay off the ground until your landing spot is past your rear wheels, then gently release some of that pressure to touch down.
Try this approach and just see how long you can keep it off the ground. See how far you can make the plane float. Once you've got this technique in your tool belt, PO180s will hold no fear for you. I honestly love coming in a little low on these now. This is exactly how I executed the PO180 at my Commercial Checkride.
Good luck! Maybe I'll see you in the Regionals!!