Have u tried bum rocking? I think it is from NZ baby whisperer. I have since found out that it does calm down the nerves. Baby can lay on the side or on tummy, just gently push up to rock.
This worked well with Zac too who was touchy and fluxy. Bottom patting, rocking, white noise. Z hated swings, but he loved a baby seat to sleep in, it didn't rock itself (but I could move it) or have anything distracting. (Sounds like what Katherine describes actually)
Will they take pacis? (If you want to give them) may be useful for H?
Harvey Karps 5 s work well. (Swaddle, side, shhh, swinging, sucking (paci) )