You'd want to do them on separate forms anyway. If you ever want to sell one of the items, having multiple things on one form would be a huge headache.
Yep. You must put one per form and pay the $200 per item.
Also there are several very high quality .22 suppressors that would be great dual purpose cans on both a 10/22 and a 22/45 that you may consider if you want to save the hassle of buying two!!