Guess I missed the question.  

In a Cracker Barrel, you ain't hooking up to shore power, or anything.  Same goes for Wally or Flying J.  You are on you own, no hookups unless you have a genset.

As far as the truck, it is perfectly OK to remain hitched, if you have plenty of room.  Slides?  Whole different question.  If I can put out the BR slide without impacting anyone or anything, you betcha.  Stabilizers, no.  Electrical connection between the truck and the trailer?  Depends on your anticipated power usage.  If you expect a hard power draw, disconnect the truck so you do not discharge the starting batteries.  If all you are doing is running a few lights for a short time, no problem at all to leave them connected.

In an RV Park, we sometimes leave the truck connected, if I can get reasonably level and have the length to do so.  We run out the slides, hook up whatever we need and enjoy.  Even for a one-night stand.

We stay hooked up I may if there is wind run the stabilizers down until they just touch at most take a few pounds off the pin.

Mallo

I have never stayed overnight @ Cracker Barrel, Wally World, etc. but I have boondocked & stayed in rest areas overnight.  I wouldn't extend the slides @ Wal-Mart or Cracker Barrel since it may look like you intend to stay put for more than one night. 
As for leaving the RV attached to the TV, it won't hurt a thing to leave is connected.  We have a list of sites (at our favorite campgrounds) that are level enough to leave the TV hooked up, this works great for us since we don't do a lot of exploring when we camp.  It is a good idea to drop the front jacks to take a little of the load off of the TV and steady the RV a little too.  53 Merc gave some good advice on the power supply; I always disconnect the wiring to prevent a dead battery on the TV.  You can buy and install an isolator (SP??) to prevent that from happening. 

When we one night stand, we usually try to find an out of the way parking spot that will allow us to run out the slides (ours are on the drivers side). We don't disconnect or unhitch from the TV. We always get permission if it's a retail business other than a truck or RV supporting business.

We don't put out chairs or mats and leave the space clean. My old truck did leak trans fluid, just a few drops, so we would not park where this would be an problem.

If we stop early and would be walking around in the 5th wheel I would put down the landing gear and stabilizers. We would run the generator as needed or for the evening while watching tv as long as it wouldn't bother anyone parked next to us...fumes or noise.

If shore power available will hook up to it especially if need A/C to stay cool or heat to stay warm. Again this would depend on if we were stopping late and just going to sleep or early and need power for cooking and tv.

Have had one night stands at wally world, gas stations, shopping centers, side of the road, city hall parking lots, public parks, friend's houses, repair shop and all the usual places like truck stops, rest stops & camping world.