Could a man be so skinny he's unable to make a baby with a femme?

Skinny? what does that have to do with being able to get a woman pregnant. And a 'femme' would not be used for a straight woman.

You are a very strange person.

I'm sure there is some limit where a man would be so emaciated that his body starts shutting down - leaving him incapable of getting/maintaining an erection and/or producing sperm.

Other than that, no.

No. Weight has no effect on fertility nor does it affect sperm count whatsoever

No, that is a matter of infertility,a sperm count, can tell that.

What is a femme besides a lesbian role? Female? Are you asking if body fat affects fertility in men? All I can find it being overweight lower your sperm count. Nothing about anorexia.

Skinny as in having a narrow waist and thin arms and legs? No, that wouldn't prevent making a baby.

Skinny as in having a narrow penis? That actually won't interfere with making a baby, either.