Boy, this baby is giving you a run for your money, isn't he?
Sounds like the movement helps lull him to sleep, but you don't want to rely on the car and the swing, and that whole "sleep when the baby sleeps" goes out the window if you're behind the wheel or behind a stroller! My kid was super sensitive to stimuli, and we got a hand-me-down teddy that had one of those mother-heartbeat-sound simulators inside. We eventually cranked it up to full volume. I'm not sure it was the heartbeat so much as the white noise aspect. Even as a toddler, he slept much better when we had a constant noise in the room. Can you try one of those inexpensive white noise machines, or an allergy filter thing? I'm not sure they are great at removing allergens, but the constant noise is great - we found one for $10 on clearance that was cheaper than the replacement filters for the old one! They block out the traffic noises, the sound of moms jogging by or kids waiting for the bus, someone closing a door, the TV, the house creaking in the wind, and so on. (A fan can work too, but then it blows everything around and the draft can be annoying.) I realize it can make him, and you, a little dependent on it, and it doesn't work during a power failure, but for a kid with an older sibling and a very tired mama, it might do the trick.