Andy you are doing great. This early in the year I just work on my form. I don't worry about clothing or my quiver till that last month before the season opens.
I mostly try to shoot from different body positions, I shoot from my knees out to all ranges.
The heart rate thing is a good idea. I try to shoot first thing in the morning, Half a sleep no coffee, in my pj's ,no warm up.
Don't know if it helps but what ever gives you confidence.
Btw your body knows your 45...... your brain ain't giving in yet
Tight groups.....Os