Mr. Fix-it is now a fixture at our house

A tide clock breaks: Mark orders the replacement parts, dissembles the clock completely, puts in the new works, checks the tide charts for Wellfleet bay, and returns the clock to its owner with the clock's hands telling the morning and evening tides. A pull-string from our bathroom's mini-blind snaps, and before I can blink, Mark's got the shade down with the cover off as needle-nosed pliers in hand, he re-threads the cord through the minute hole and suddenly we're in business again. The soap dispenser under the kitchen sink stops working, and Mark slithers backwards into the chasm under the sink to discover that a little plastic part has broken; if he could get another, he'd fix that, too.

Who is this man? And what has happened to my husband?