I have a few thoughts. First, I agree with Ryleighgirl, you may want to start all over with a new word, maybe "here" or pick a new word, and only use that word outside, and make coming to you totally worth his while, make the reward a huge bite of great chicken or hot dog every time he comes, and make your voice really exciting (not demanding) - then release him to go back out, don't always make "come" mean he gets his collar grabbed and has to go in the house. He may be equating you saying "come" with fun being over, and who wants that? He's not being stubborn, he's being smart. I don't think dogs are deliberately stubborn, they just like to have fun, and do what works. Make doing what you want, worth his while - it will turn out to be a win/win for both of you.
As far as cranking that collar up as far as it will go - think about the pain you're inflicting (it obviously is, if it's making his back leg shake) and the damage you could be doing. You said he just stands there and twitches until it stops. He may be unable to move he may be shocking so badly - have you ever thought of that? Cruel and unusual punishment, if you ask me. What scares me more is that you say you've put double shockers on him. Try it on yourself just once around your own neck and see what you think. And don't say you HAVE to do it, there's no other way, and it's his own fault. Again, it all comes back to training.
Here's where my next thought comes in. I know you said you have 3 acres, but .. does he ever get to go out on walks outside of the fence and explore beyond the fence? Yes, 3 acres is a lot, but obviously, he'd like to see what's outside of that area. He keeps proving that to you. As Fickla said, 3 acres and a fence is not an excuse/pass from exercise. He's 1-1/2 yrs old - that's very young, he's an adolescent. Standard Poodles are very energetic dogs, they need lots of exercise. Just the fact that he has a lot of room where hecan run around, doesn't make up for a good walk with you... outside of that fence. A nice hour walk, where you two, together, as a team, can explore that area that he so obviously longs to see, might take away some of his desire to plow through that fence - cuz he knows the two of you will be walking out together. Also, do you ever work his mind doing things like trick training? Again - you have a very bright breed that needs something to work that mind. If you don't give him something, he's gonna find something on his own. He's proving that. Again - not stubborn. In his mind, resourceful. Does he like to play ball? If he had loads of exercise playing ball, chase, whatever his favorite game is, a long walk, and a couple sessions of learning a new trick every day, I bet he'd be more inclined to stick around home. He'd be much more tired, more fulfilled, and hey, he'd never quite know when something fun was about to happen at home - could happen any time ..... better not leave, we might be playing ball in a minute, or going for a walk, or playing tug, or getting out the bait bag to learn a new trick, or .... better stick around, don't wanna miss the fun! Make home be the place he loves to be more than anyplace else! Just a thought.