any way to divide an order to get separate labels?

I offer an add-on product in my store that's designed to go with my primary product and I expected people to just add one add-on per order but somebody ordered my entire inventory. Which messed up my pricing model because normally I could do it in an eBay standard envelope for $.74 or $1.03 but shipping my entire supply bumps it up above 3 ounces and I'm gonna have to pay six dollars in shipping and I'm gonna lose money with this order. Now I can divide it between two flexible mailers for $1.03 each which would be a total of $2.06 shipping so that would be helpful but the problem is because this person ordered all six and one order eBay only wants to sell me one label.

QUESTION: can I use the "get another copy of a label" to create two labels to ship this into packages to keep the weight under 2 ounces per package? I don't imagine that would work because I would only be paying for once so after it scanned the first time I think the second package wouldn't travel.

QUESTION: is there any way to divide this into two separate orders? Then I could buy two separate shipping labels?

QUESTION: If I can only get one shipping label for eBay can I get a shipping label from someone else or somewhere else for the second package? I guess maybe through hostel service? It wouldn't have tracking your insurance but at least it wouldn't destroy my profit.

LAST QUESTION: How can I prevent this from happening again? How do I limit to three items per transaction/order but still maintain a quantity of 18 total? I don't mind if one person buys all 18 just as long as each set of three is in its own order for postage reasons