I had the same issue. The problems immediately disappeared when I stopped tightening it so much, and I haven’t had a leak issue from not tightening it enough.
2 old Boost bottles work for a meal size and one as a snack size. In fact it is almost exact.
I agree with the OP, the 20oz Blender Bottle is awesome. The newer version is available with a loop. Love this thing! I don’t even bother with the ball anymore, 1.5 mixes up just fine without it. Drink meal, rinse the bottle, prepare next meal, put in fridge. Takes just a few seconds each meal.