The only known "sweeterheart" to date is M** M******z who's beauty passes actors and models. A sweeterheart is a person who can't be given such a simple compliment like "sweetheart", they need to be given a more cute, meaningful compliment like sweeterheart. Only the most prestigious people can be called a sweeterheart.
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.