OP, howdy and welcome to the forum.
For the most part, I agree with Endiku and NorthernMama, you and this horse are a terrible fit right now and I really suggest you avoid trying to handle him in any way without an experienced person right there with you. Truthfully, it would probably be best for both of you to part ways so that you could eventually lease or buy a horse more suited to your ability. BUT, if you're dead set on having this horse, then you need some professional help to keep you from getting hurt.
Where I think you should start is with some lessons from a good instructor. They'll often have good natured school horses for you to learn the basics with (horses who are unlikely to injure you in any way unless they accidentally step on your toe
). After some time spent there where you can learn how to handle a horse properly and you gain some confidence in your ability
to handle one, then you should talk with your instructor about working with the horse and then with you and the horse together.
If this horse hasn't been touched for years, then he'll need a training tune-up before you do anything with him anyway. Though it really all depends on what quality of training he had in the first place. IME, with Amish horses, it's rather hit and miss; some are really great and others....not so much. Depending on his training, it may take more time and $$ than it's worth to get him to the point where he's suitable for you. Or, he may never
be suitable or safe for you to handle without experienced help present.
Another thing to consider is that Amish horses don't get loved on. They aren't petted and scratched and pampered. They are tractors and cars that get caught, they go to work, they get turned loose and fed, then tomorrow they do it all over again. They are work
horses, not pets, so he may have never had anyone who wanted to love on him before and he's probably not sure how to take it. He may never
like it. Some horses don't, regardless of how much time is spent with them or how much training they get, some just don't like being touched. They have an attitude of "Let's just go to work, let me do my job, and leave me alone".