I've been working on getting through a mental block my mare has. When I had her years ago she would jump like a dream. Loved it. But when I moved away I don't know what happened, I suspect she was ridden in a harsh bit and caught in the mouth a lot. She had just completely shut down. I couldn't even get her to walk over a pole on the ground when I started riding her again.
When I ended up doing is the same as you are, playing follow the leader. She will follow me over anything including jumps.
When it was time to work under saddle I would just put poles in random places around the arena and we would walk and trot over them, eventually cantering. I made sure to make a big deal out of going over the poles. I carry sugar cubes in my pocket while I ride. So when she went over a few poles I would stop and give her a sugar cube.
Once she was confident with this I would put up a small cross rail and have the poles, trot in front of the cross rail, past the jump and praise. Then trot over the cross rail. The biggest thing is making sure its not a big ordeal, you don't make a big thing out of prepping to go over the jump. Its just "okay lets go" as you trot around. She goes over the jump and I keep her going over some poles then take a walk break, sugar cube.
It was a long drawn out proccess that took me a few months. As time went on I would add more cross rails, bump them up to small verticles and keep going. I would cut back on the sugar cubes obviously, she would do a grid then get one when we went back to walk. Then worked up to courses.
I just had to make sure every time she did it correctly there were big praises. Also I know a lot of people will roll their eyes at this, but I refused to smack her with the crop when she stopped. I would just go "okay fine" I would stand her in front of the jump for a minute let her realize its not a monster then circle away and she always would go over after that. Now obviously if i'm getting some dirty nasty stops that are just simply "no I don't want to" I would give her a tap with the crop and go right back at the jump.
The most important thing is make sure you are 300% commited. No second guessing, no letting yourself go "ugh he's going to stop I just know it". You go out, keep your leg on, keep your eyes up and focused on something on the other side of the jump and commit yourself and your horse completely. Because of his lack of confidence he needs his rider to be confident. Another thing is don't go into two point two strides away. You go into two point AS he is taking off and release over the fence and keep the release until all 4 feet are on the ground. You need to guide him and hold him into the fence but never ever ever catch him in the mouth on the landing or your progress will go back a step.
Like I said it took a long time but a year later I have her confidently jumping 3'3 jumper courses and we are going to start cross country this summer.