Transition to crib

We are doing better after last week's plague, thank goodness. Now on to bigger and better obstacles.
Since HM was born, he has slept in his swing. Not actually swinging, but just upright. When we put him in his bassinette in the hospital, he hated it from the get go. The nurse told us he had reflux and propped the bassinette up a bit, which helped, but he still hated it. So when we got home, we found out AH HA! The swing works great!
Now we are 4 1/2 months down the road and our lil man is growing out of the swing. We'd been noticing that he was increasingly uncomfortable in the swing, and finally got to where he'd put his feet on the bottom and push. So, listening to our child and dreading what we were going to hear, we decided to bite the bullet and transition him to the crib.
It hasn't been as bad as we thought it was going to be. HOWEVER, we are still dealing with him holding his legs up. He holds them up all crumpled close to his chest. Then when he relaxes, he wakes up. Then he starts rocking back and forth, accompanied by some agitated sputtering which escalates to screaming if you aren't fast enough. So we swaddle. He loved swaddling when he was born-2 months old. Then, I guess we didn't have the need and discontinued it. So now, we swaddle him to avoid the leg chain reaction, but it still happens. So my lil guy that was sleeping so well throughout the night for about 6 weeks is now NOT SLEEPING as soundly. I thought we were smooth sailing. I was pinching myself that we'd made it. NOT SO FAST, MOM!

So any and all advice about this issue is appreciated as we navigate this latest adventure in parenthood. Last night, his uncomfortableness was compounded by the fact that he had to have 2 shots. But my 18week old weighs in at 15 pounds and 25 inches. He is in the 50th percentile for height, weight, and head circumference. My lil textbook baby! And he is eating bananas, avocados, butternut squash, and cereal now. All in all, this journey is joyous!