Sooooo senpai had feelings for kouhei?

How did you come to this conclusion? I didn't pick up on it at all

http://www.mangago.zone/read-manga/papa_no_sukinahito/uu/ibx_chapter-3/pg-26/

I think it can be read two ways. Either he liked Kouhei too, but unlike Tomoya he gave up on it

Or he loved Tomoya, and knew Tomoya loved Kouhei, so he gave up on Tomoya and helped the two of them