I agree - when he stops and tenses up like that, get him moving. I've found that when they're really tense like that and the barn is #1 on their mind, circling them frequently gives them an excuse to try to cut in and collapse the circle and head for home, and gets them more worked up when you try and fight them and aren't going anywhere. I always want to get them moving forwards when they want to stop, into a strong, forwards trot if you can. It helps to ride a lot with one rein so they can't brace. Keep him going straight and forwards until he relaxes even a bit before you take him home.
You should be really tall and strong and square and keep him really straight between your hands and legs, so even if he did try to duck or spin or go sideways or stop or even jump something again, you'd still be centered right above him. A strong, deep, unmovable seat is what has always given me confidence (in addition, of course, to knowing and learning how to handle a situation that may/will come up). I know you were alone - is there someone you can go with, at least a few times, that will help keep you calm and relaxed and confident? It'll be much easier to get him over his anxieties if you're not nervous or apprehensive.