I'm surprised you've had issues with the meridian, we love ours and never had any issues & our kids are about the same age so you'd think it'd be the same batch.
For him getting his arms out, some.kids just do it, regardless of the seat. You can buy a Houdini strap that clips the shoulder straps closer together so they can't get their arms out, looks sorta like the chest strap on a backpack.
I also recommend crep website, they rate them on ease of use as well as safety.

sent from my watzamajig so may not make sense....