Honey, this is what you are calling a panic attack. It's not. It's a tantrum. If you think that an 11 month old can't have a tantrum, you're naive. (It's okay to be naive about kids. It's not like we automatically know everything just because we give birth.)
Your child has figured out what works. What works is that he scares you into giving in to him. You've already allowed him to rule the roost with all the attention your husband has given him, sitting with him on the bed. Therefore he doesn't know how to self soothe. You will either have to let him learn, or you will not sleep.
If he will not stay in the crib and can climb out of it, then you have to remove the crib. Put the crib mattress in the floor and baby-proof the room. Either use a baby gate or turn the doorknob around so that you can lock the door from the outside. It is a SAFETY ISSUE, preventing your child from wandering the house at night. You mustn't let him do that.
If you think that you can get him to sleep in the crib, and if you dearly want him to continue for a while (the best thing for you all), try this for an entire week. When he starts screaming, either you or your husband (or take turns) go in and sit on the floor and put your hand inside the slats and touch his leg. DO NOT PICK HIM UP. Do not talk to him. Don't have eye contact. ALL you do is touch his leg. At some point he will lay down to be closer to you. Let him cry, cry, cry. Don't do anything but touch his leg. This "panic attack" is a learned behavior. That's all it is. You have taught him that it works. Now let him learn that it doesn't. It may take HOURS before he goes to sleep. Make him get up same time every morning and only nap as long as he is supposed to. I promise you that the crying jags will get shorter if you are 100% consistent about all this. And in a week, you won't be spending nearly the amount of time you are now cajoling him to sleep. Eventually he'll stop waking up.
The other thing doing this will do is teach him to stop acting like this with the crying. You need to IGNORE this kind of behavior. If he throws himself in the floor or does anything to scare you, put him in a playpen and just go about your business, pretending that he isn't crying. Put earplugs in your ears if you have to. When he stops crying, come over to him and pick him up and give him hugs and give him a toy to play with. DON'T give in to what it is that he wanted before.
After he learns that the "panic attack" mode doesn't work, you will be better able to do what most parents do with a child this age - re-direct, re-direct, re-direct. And when YOU stop acting like your child is having panic attacks, you'll all be happier.
Truely, mom, children WANT limits. They need them, that's for sure. But if you don't provide CONSISTENT limits, they will wear you out with constant and illogical demands. You don't know that yet because your child is too young to do this, but keep up what you're doing, and this is what you will have.
Good luck...