Only love songs? Then define "love songs"; for yourself
I mean:
- songs for romantic dinner?
- cuddling?
- slow dancing during party?
- having sex?
- f-king?
That at least 3-4 different categories
Do not rely on some genres labels, do not use BPM. Just make your own categories. You can start with something like a point system, rating from 1 to 10, going from soft to hard; and with time choose how many categories there should be and marge in one those with 1, 2 and 3 points. You can choose just that or add also the second rating for tempo [but just do not count BPM /t/17133/1]