A chumpin is a round-faced person with a very chumpinesque smile, i.e. a smile with puffy cheeks that makes them look slightly dopey but endearing all the same.
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.