I think that after Fai's conversation with Yuuko, he has accepted the fact that he has gotten close to the group, and that his pain is theirs as well. To me, that conversation marked a "transformation" in Fai's actitute. Right after they finished talking and Yuuko told him about Sakura going on her own, he reacted in a completely different way he normally would. Under normal conditions he would wait, maybe say a thing or two, but never getting too involved in the situation, but instead he just went mad trying to look for Sakura and scolded Kuro for letting her go....
To me, that transformation was really noticeable
So what i'm trying to get to is that maybe he WAS mad at Kuro for saving his life, but not anymore. He just got pissed at him for letting Sakura go on her own to find that egg. When the time comes to drink his blood, I think he might hesitate and probably discuss, but in the end he will do it cause he has already accepted the fact that the gang is like a family to him. Is he avoiding Kurogane? I don't think so, he's just taking care about Sakura just now