The basal metabolic rate doesn't matter at all.

You want the Total Daily Energy Expenditure (TDEE) which is all the energy you use in a day. Tracking your calories and changes to your bodyweight lets you do that. (You'll want to use weekly averages of your bodyweight to smooth out fluctuations that don't reflect changes in tissue.)

Yes strength training with sufficient protein is a signal to your body to maintain or even build muscle mass, so every pound you lose will shift to mostly or entirely fat.