Don't make deals with a kid who doesn't want to do what he's supposed to do. He's not going to Target or playing video games or riding his bike if he stays home from school. School is school.
If he gets undressed, take him there in his pajamas - I promise that will only happen once. Show him you mean business and he doesn't get to bargain for everything or get a treat if he complies with the basic rules. Get him to bed on time and up on time for a certain amount of procrastinating - it's completely typical. But he's holding you hostage to the schedule and you can't allow that.
I agree with not pushing the potty training. He's on the road to getting it, and it's fine.
I'd stop with all the reassuring that "you love school" - that's not his problem. His problem is he doesn't transition well from one thing to the next - from home to school, from breakfast to getting dressed, etc. So don't delay his "must do" list in the morning - stick to priorities. He gets up, gets dressed, eats breakfast, gets his backpack ready, etc. If there is still time, then he can read a book or do a puzzle - anything that can be stopped in the middle, but no TV shows that don't end in time for him to avoid being late. If there is any early drop-off or other activities for 15 minutes as kids are arriving, get him there on the early side instead of waiting for the last minute and stressing about being late.