WELL. Layla is... probably actually more fond of him than some of the other Inner Circle members right now. Or most DEs that is. She also gets on well with Mitzi still so there's that? Which. You know. Likely to change incoming. >_> Feel free to try and manipulate her as you see fit, Winthrop (and probably have in the past to coax her on more).
Given he wasn't a Slytherin I assume Aberforth doesn't actually suspect him of being a DE unless you think that's obvious by this point. BUT anyway, Aberforth will happily clash with all Original Knights members. >:]
Lakshmi is apparently a terrible judge of who is a DE and who isn't so she'll think he's a bit odd with the graveyard thing, but otherwise he's quite nice! She's also probably aware the Abbott in her nieces' class is a sweetheart and applies that to thinking Winthrop is a good person too given how he acts. Good work, Lakshmi.
Angelus is totally fine with him/would respect him! Sacred 28 Purebloods are great. :]