1) It can't be the 6th branch of the military as there are only 4. The Coast Guard is a Uniformed Service, not a military branch. Although assets (including personnel) transferred to the Navy during times of war.
2) A branch can't be created by Executive Order. It's that simple. We'll see how the midterms end up, but it might not be the cake walk some seem to think it will be.
3. I'm personally not opposed to having a Space Force. But the Air Force already has that covered so instead of a new branch, just transfer the Air Force's fixed and rotary wing assets back to the Army, Army transfers it heavy rockets to the Air Force, Air Force renamed Space Force.