It’s $50 to have it rescored. If your score goes up, you get your $50 back. If your score stays the same, they keep the $50. (Everything I’ve seen indicates that your score will not ever be lowered.)
Lots of high ACT scorers get int he 20’s on the writing, so I wouldn’t worry about October. Only about 1600 students each year get a 36.
No.
35 is still a great score. No reason to even send it unless a college requires all of your ACT scores. @CGHTeach is right that they will never lower a score.