Basic groundwork question?

After years of not really having to do anything when asked, you are now trying to make him work and he's saying, "I don't think so and you can't make me." No offense, but you are not the person to teach this horse to respect the human - he needs someone with more professional experience who can correctly and humanely push through these bad habits. I agree - he is now a big, stubborn horse and you could end up getting hurt. My advice is to send him to a professional trainer and once he's got some manners, THEN start working with him and the trainer.