I pre-press without any heat. I have a 600lb hand clamp I use with a 1.5x1.5" mold to form the pucks.
I’ve never tried bottle tech, but hear that’s the way to go with no pre-press necessary.
I am certain it is your flower and not your technique/equipment.
Yes you can reclaim quite a bit from the bags. I like to remove the weed puck from the bag and rinse the bags in alcohol for about 5 minutes. I then evaporate the alcohol and use the remaining resin for edibles.