J.T.
i think we can all relate to what you are dealing with in one way or another, at one stage or another of development. so, first, take a deep breath, this too shall pass!
so, as far as what to do about it. my #1 rule when my kids are acting up is to make it THEIR problem. so, in the situation you are describing, i'd start the "getting ready to go" process about 30-40 minutes earlier than usual. this means he loses that time that he would normally be playing, watching tv, etc. and i would say "okay, since you're not listening to my directions anymore, we aren't going to have time to watch tv in the mornings anymore since you are causing us to lose so much time with your behavior". i would start the normal routine, and try to give choices where you can. i can take the tension out of a lot of situations by offering two choices that are okay with me, then my kids feel like they're "in control" of something. the minute he starts acting up, i'd just strong arm him and dress him/get him ready yourself after giving a warning/consequence(ex: if you choose to not put your coat on right now, you will not be allowed to "xyz" tonight) - the STICK TO THE CONSEQUENCE, not matter HOW well he is behaving that night - he is old enough at this age to remember why he is being punished. on the other hand, you could say "if you cooperate very nicely and do what i ask, you may play your leapster/ds(if he has a video game thingy) in the car on the way to school/church, or you may have a bag of fruit snacks in the car". lots of different ways/punishments/rewards to help with stuff like this. hope it improves soon - but give yourself enough time to discipline and make this HIS problem rather than yours. good luck!