Depends on how the fuel with Orin did go, since that will basically decide Durges fate.
I won against her and denounced Bhaal, who killed me, then Withers came and revived me and said that I am free of Bhaals taint. That Durge did go adventuring with Astarion after the ending and at the party they both talked about how great of a time they had. So I guess, that's the happy end, going with your love interest on adventures ( or cottage core, if you romance Shadowheart) and live a normal life. People were speculating, that Durge became Jergals Chosen with that, but I don't think that is the case. He gives them a chance of a normal life, nothing more.
I don't think, the three Stooges are completely gone anyway, so if you have the unlucky ending, when you didn't win against Orin or go against Bhaals wishes, you probably will still have a miserable life.
