Steal once:
-lose disposition from the shopkeeper, as he suspects it's you/he's in a bad mood.
Steal four times (with the equivalent of 4000 gold worth of goods)
-shopkeeper goes out of business.
I don't llike your 1st and 4th penalties at all. If the shopkeeper saw you, he should call the guards. If he didn't then he shouldn't know. I don't trust Bethesda to walk the line between the shopkeepers holding a small grudge against anyone who shopped the day items were stolen and the shop keepers having psychic powers that tell when you stole from them and magically tell/convince every other merchant throughout Skyrim.
I like the idea of guards staying around, or the merchant getting a better lock for his door. Maybe some excentric potion maker could put traps in his store at night.
Instead of making the store close at the 4th offense, I'd much rather just see the merchant lock all his goods in a cellar/attic/closet at night and start sleeping in a chair infront of the door. But closing the store down for doing what some people have their entire character geared to do? To harsh.