ethan.. what is your hatw, atw and htw records..?
i've done 20 htw though I can't do 20 each try, 28 atws and 8 hatws and I'm no were near your level in lowers. I can hardly do amatw weak foot or tatw weak foot, it's annoying as hell. probably because i find it boring to practise them

Anyway something I used to get better htws was to do a htw motion several times with one foot like -
Htw - inside atw but as a htw motion I did this with both feet and now I can do 5 just popping the ball up with only my weak foot.
I felt this improved stamina and concistency.
I also just simply tried to improve my record every practise first set it at 8 - 10 - 13 - 15 - 18 - 20 and so on.
for hatws i don't really know anything that will help other than practising them.
and for htws maybe this isn't the correct way to go, this is just what I found helped me.