Ambiv, you can appear relaxed and flexible, but if you need to study on a certain day, you can let him know what is more convenient for you. And if you are uncomfortable with swapping cars in the school parking lot, suggest some other place and just simply say that you would prefer that other place. You definitely can go with the flow, if you feel like it. But if it creates some inconvenience for you all the time, you need change that. I know it could be difficult, but in the long run, if you always accommodate to his schedule, he will start taking you for granted.
M:50 H:52 S28 (my S from previous marriage) M:17 + 3 BD: 06/12 S: 06/12 - H works in another state