Yes, I think buttload is an acceptable, informal substitute, at least in AmE. However, some might still find the usage of butt somewhat offensive since some people consider butt to be a mild curse word. These people might include parents with very young children. Even so, I think most kids, teens, and adults wouldn't mind. In any case, a few more casual, inoffensive examples include
- ton - a great quantity : lot <ate tons of cookies> <has tons of money> <a ton of work to do>
- boatload - an indefinitely large number <a boatload of money>
- load
- often loads Informal A great number or amount: There were loads of people at the parade.
- lot
- a lot or lots Informal
a. A large extent, amount, or number: is in a lot of trouble; has lots of friends.
I think love interests or romantic interests could work, given OP's latest context.
From tvtropes.org,
Love Interest
The princess to be rescued, or the Prince Charming to sweep the heroine off her feet. Or just someone that happens to become romantically involved.
It's a Super Trope so universal, that there are too many specific examples to list. There are a few in the list below.
The list includes Girl Next Door, Girl of My Dreams, and Hello, Nurse!.
When applied to real life, I think love interest is just as flexible. A love interest is basically a person that you are romantically interested in. This could range from something small, like going on a few dates, to something big, like love and marriage.
A romantic interest is similar to a love interest, with the possible nuance that a romantic interest concerns more casual relationships.
I wasn't able to find any reputable dictionary sources, so I imagine that the definitions vary from one person's opinion to another. However, if you call these girls your love interests, I think people will get the point that you are interested in them romantically or that you pursuing them romantically to some degree as described above.
By the way, you could also say that you are interested in these girls, or into them. They mean that you have a some kind of romantic interest in them, though it suggests a casual one. I don't think it would include "loving" someone, unless it's unrequited love.
Best Answer
Calling it a notch would be fine.
The scientific unit of measure is a decibel, but that isn't something you would say unless you're talking to someone who knows what it is, and you know how that correlates to the gradations on the remote control.