Hmmm. Sounds like Kuroi's getting stood up a lot.
Would you prefer he cool it on contacting new women to date? Would you rather he worked on issues in his relationship with you (and Momoiroi) first? If so, have you told him that? If you did, what was his response?
I get that you're sick, but it's not like Kuroi has no self-control. He should be able to hold off on contacting new women if you ask him to. Polyamory isn't going anywhere. It'll still be there after you get feeling well and he gets done working on his relationship with you (and Momoiroi).
I'm hearing that he's done some kind of damage to his relationship with you? How did this happen, and what needs to be done to fix it?
Love means never having to say, "Put down that meat cleaver!"