Hei will definitely get his powers back because Suou isn't going to shoot anymore. I think it's a simple matter of somebody from that party has to do the hitting. Also, this is a show about contractors amongst other things so what's the point when none of the protagonists use their powers
I really do think that Suou is in the process of developing feelings for Hei but as she has clearly stated herself she really doesn't know what it is like. There is a clear stage in their relationship in this episode. Hei called Suou by her name which she appreciated, him cooking and taking advice from her and actually allowing her to go with him to shop.