Mc is derived from the American fast food place McDonald's. Whore is derived from old english. Mc specifies that it is a food. A whore is a woman/man who engages in sexual acts for money. So a mcwhore is a whore on a bun with toppings served to you easily.
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.