Use a candle and a spray. You also shouldn't get bites inside your tent.
Fucking how? Also, if your backpack has food, it should either be in your car, suspended in the air between trees or in a locker provided by the campground.
See 1.
Tarps exist for several reasons, putting them above your tent and your eating area is one of them.
I used to be of the “just sleep on the ground, it feels fine” mindset. Then I turned 30. My back doesn’t like sleeping on the hard ground anymore, but a cot is perfectly comfortable.