As far as I know they both give into each other. For the sake of each other.
I'm not going to get throughout into if it's rape or not, but he did have to have sex with him for him to survive? Which I guess depending on the person and their morals could justify it. After he awoke though, I'm not 100% if he still needed to have sex with him or not, if he didn't that's where I think it's considered rape, though softer than actual rape that's drawn in yaois a lot. He clearly wasn't in the right state of mind, and therefore can not give consent. It's the same logic you use for drunk people. If a drunk person forces them onto you, that shouldn't be considered consent.
Hen loves Ivan so much. Can't they just cut off that stupid mark so that Alex could be on his merry way?
I think the author wanted to pull stupid cliché stuff while she could use the mark card. Now that she got what she wanter, aka this shitty scene, the author will probably get rid of the mark