Are there locations locally where you can purchase propane for a camping grill or heater?

Shree's .... yes

Bring everything with you. The teeny tiny towns dont have much to offer as far as supplies

There is a small market in Wanapim 12 min away that sells propane tanks.

It is pretty isolated. There is a general store at amphitheater by parking lots. Card only- no cash. There are a few gas/general stores Shree's having the most provisions. Propane, food, etc. The store across from Shree's has a mini liquor area as well.

Yes. Any local gas station.

There's a store on site but I can't remember if there's propane. You probably wanna hit up Walmart first anyways lol it's super expensive. I paid $8 for a $2 Walmart pillow there and $9 for a $4 beer.

Not really much out there