Yeah, Winslow can see right through May. Maybe he's perceptive enough that just one session at a self-help group has taught him everything he needs to know about how her mind works or maybe May is just that bad at hiding herself. May's reaction shows that he is right on the button though!
I think we can definitely say that Jeph has sunk the Sven/May ship but that isn't a surprise to me as I always got the feeling that it was all more curiosity and bravado on both their parts from the start. It was also, strangely enough, a reminder that Sven has changed a lot and he's become a much nicer guy since he blew his chance with Faye (possibly with Hannelore's help).
I'm pretty sure that we're at the end of this arc but I'm thinking that it isn't impossible that things may yet get more... complicated between Winslow and May, depending on how far Winslow is willing to push this even though May's now getting defensive. Winslow also has yet to say hi to Momo and Pintsize, so that may happen next week too.