I think it's a pretty reasonable character as a baseline, depending on how much you keep in mind that this is King of the Hill.

Most of these guys aren't exactly rocket surgeons. Hank is pretty successful and a good dad, but he's also a bit of a dolt and not Incredibly Successful just normal middle class successful. Peg is pretty much hot garbage, and not physically hot. Bobby aint right. Luanne is borderline retarded. Dale is a paranoid conspiracy nut married to a hot but trashy and unfaithful wife. I think she was a news reporter. Boomhauer is basically just a weird horny drunk (and also a government agent). Bill is Bill.

The Laotian couple, Khan and his wife, are probably the most successful and they're still pretty dysfunctional.

Jack is impulsive, distrustful of authorities and "experts." Seen as a conspiracy theorist but he's done his research. Speaks his mind, not particularly subtle. Doesn't like prejudice. Does what he thinks is right. Independent journalist. Martial artist. Lots of guns of varying legal statuses, loves mostly Metal.

(By the way WanderingDragon I noticed you like Dimebag Darrel. Check out Damageplan if you don't know about them)

I think he can be a pretty damn good fit all in all.

Here are ways I would consider going with this character if I was writing him...

Jack just got hired by Arlen News to be a Local Story and Public Interest guy. Him and Nancy don't get along. He doesn't like having to cover bullshit minor Public Interest stories when there are bigger stories out there to crack. All kinds of conspiracy theories he wants to investigate. Intersects with other characters as a result of his job. Has to go report on the new barbecue Strickland Propane is promoting. Or he has to report on the customer at Sugarfoot's who says he saw the face of his Great Grandfather in a piece of toast and the town is split about whether he's crazy or it's an act of God.

Jack is investigating a grand conspiracy about Arlen. Maybe about old Arlen history or about Strickland propane or about some big government cover up of something or other. Maybe he came across Dale Gribble on some deep web site and is convinced Dale "knows too much" and is actually a fed trying to do something insidious. He could be spying around town trying to gather information but drawing too much attention to himself due to him being impulsive, fighty, and Arlen being a fairly small town.

Jack is writing a book and has decided to focus on Arlen. He's going incognito, he's going deep cover, he is doing the journalisms. Trying to convince these backwood bumpkin ass hillbilly inbred etc etc that he's one of them...and in so doing realizing they're not as shit as he expected.

Maybe a drinking problem.
Maybe a DUI.
Maybe he gets into a big dustup and ends up in the Arlen County Jail.
Maybe he starts a Fight Club.
Maybe he goes to music shows and sees John Redcorn's Band or Bobby's Band or Connie's Band or Joseph's Band. Redcorn had similar musical tastes, I could see him or his son being into the same stuff as Jack.
Maybe he runs in to some of the cast at a gun range. I could see Dale or Redcorn at a gun range. Joseph too. Hell all three together.