1. Where a seme is popular with girls/women but rejects them because he's actually secretly in love with the uke who is unpopular with girls/women and envious of the seme.

Bonus points if the seme always seems to steal the girl/woman that the uke has a crush on or wants to confess to.

2. Where a seme holds a uke captive (plus rape?), maybe because of a debt owed by the uke or his family. The seme's always been secretly in love with the uke.

Bonus points if they're childhood friends.

Erm I think Aitsu no Daihonmei would fit the first one. It's quite a unique manga. Not everybody's cup of tea though I would say.
I'm sure I know some more that fit number 1 so I'll edit this later when I find them.
Edit this one might be good. The uke is not so much unpopular but there is a definite gap between the two and tension if I remember: Tonari ni Iru no ni, Tooi

1. Where a seme is popular with girls/women but rejects them because he's actually secretly in love with the uke who is unpopular with girls/women and envious of the seme.

Bonus points if the seme always seems to steal the girl/woman that the uke has a crush on or wants to confess to.

Maybe, Yamato Nase's Saa Koi ni Ochitamae?

2. Where a seme holds a uke captive (plus rape?), maybe because of a debt owed by the uke or his family. The seme's always been secretly in love with the uke.

Bonus points if they're childhood friends.

A manga that came into my mind is Haruka Minami's Saihate no Kimi e.

I don't really like these two mangakas when it comes to plot but Saihate no Kimi e really checks out what you're looking for, at least i thing it does. And it has a pretty good plot too, very dramatic. They're both okay though. Hope this helps 😀

The second one sounds like Okane ga Nai lol... minus the childhood friends thing. I personally find it too much though (it's so sterotypical some argue that it's a parody of the yaoi genre) 😛