Here's What We Saw in Act Three

In Act Three we return to the Gothic splendour of New York where Brian has become a freakish bourgeois poodle.
He is paraded around the art scene.
Brian realises that his relatives were right about sticking to his own class as art people are patronising. He stamps on the artist's toes, slaps his face, and kicks him in the arse, propelling him into a modern sculpture - literally kicking his arse.
Brian leaves Bonnie, telling her that he left a can of Spam in the fridge. He makes a joke about something called "brewer's yeast". She slaps him in the face. Brian tells her that, 'everything ends badly, otherwise it wouldn't end at all.'
He searches out Jordan. She throws food over him. That pimply kid from the Simpsons laughs at him. He pretends to be blind and makes it into Jordan's flat. While there he notices a painting of a waterfall - which is not their waterfall.
She tells him she is knocked up. Brian visibly reels and asks if the baby belongs to him. She says yes and shakes her head at the same time, signifying both yes and no, simultaneously.
Brain asks Uncle Pat what to do. He tells him to forget about it, reminding him that she doesn't want any money. He still goes back to her apartment, and in an amazing twist, he discovers that she is a "rich chick" after all. He needn't have fretted about all that class stuff, now he definitely won't have to work for a living. Her old man offers Brian a check if he'll bugger off and leave his daughter alone. Brian tears up the check in front of Jordan but it all looks bad nonetheless. The butler comes up and tries to rough him up. Brian uses the exact same move he used on the sculptor - literally kicking his arse too.
Brain goes see Doug because it's Paddy's day and he owes him some Brandy because he lost another bet. Doug owns a yacht and stuff, but he's actually lost all the money on the market, now realising that aspiration to material wealth is pointless.
His wife is shagging everyone else. Doug falls asleep. Brian takes his wife home where she tries to shag him. Doug kills himself.
Brian realises that listening to Doug all this time might have been stupid and he should have asked his uncle for a loan from the start and opened a shitty bar.
He goes to see Jordan and there's another agruement.
Brian stamps on the butler's toes, slaps his face, and kicks him in the arse, propelling him into a modern sculpture. He calls his "joint" Cocktails & Dreams
They find out they're having twins and Brian starts giving the beer away.