1. Both materials of the DCEU and Arrowverse, and even a few others that show his clothes burn off initially, have this shown early on when he is the Flash. When he is new to the laws of the Speed Force and therefore his clothes do indeed burn up.

2. Same with carrying people and even more so for this ability. Because he usually has to learn speed sharing for this feat in order for them to be operating at the same speed as him.

3. The Speed Force doesn't fuel him like the sun. There's a difference between a force of nature and the sun. The sun as a full on star is a source of fuel within our own real world and in comic books. However the Speed Force is only kinetic energy. Which actually requires our own body's energy levels to generate up in the first place. In the end, these speedsters are still ordinary humans and therefore require energy to run in the first place.

Thank you 😊. I only watch shows and movies and was confused about it

I mean at least in the show, this was showcased in a prominent degree with Enter Flashtime.

In the comics, yes, the Speed Force absorbs friction and keeps speedsters safe when running in that regard.

Ends up being a universal feat with it.