The calculator shocked me...now I need some advice in regards to shape and bra types.

After years of shoulder and boob pain, I had enough and started scouring reddit. I found the calculator and I am not a 36-38C. I am apparently a 34F.

When my spouse jokingly holds the girls up when I'm hurting, my pain is gone. So I KNOW it's due to them.

I had cervical spinal fusions 10 years ago. So I've had 10 years of these things causing immense pain.

My questions are:

I have quite low hanging, pendulum style breasts. (I've accepted they are what they are, they fed three kids and now look like softballs stuffed into tube socks basically) What type of bra is best for that? They flop out of nearly everything. Example: I have to like fold them into anything pushup style...so that's obviously a no haha

They sag into my armpits when I sleep, would a sleep bra help this?

How accurate is the calculator? When I see an F cup, I'm flabbergasted and cannot picture my boobs in that.