Yes, multiple weapon orders placed at the same time and individual weapon orders place on different days provided 90-day and 180-day are kept separate. I currently have 2x individual gun 90-day and 1x multiple guns 180-day layaways open.

You can do them all at once. Or one by one. As many as you can afford.

Yes, you are allowed to put multiple firearms on layaway.

Yes. The same 20% or 10%(whichever layaway applies) minimal down payment applies. This can be beneficial as some FFL's will give you a discount on transfer fees when multiple firearms are transferred together.

Yes, I currently have 3 on the 180 day layaway plans.

as many as you can afford

Yes you can, fill your cart and do them all at once. Or one by one.