Sayang, what you're going through sounds so challenging, I'm thinking of you and your little one during this time.
On the pumping amount, 2oz per session is actually quite normal in the early weeks, especially when baby is still very small and feeding tiny amounts like you mentioned; some mums find that pumping 6 times a day can still build supply well over time, though of course your doctor or lactation nurse can advise if you need to adjust. For storing those small quantities, many NICU mums swear by the smaller storage bags or even small syringes, your nurse is spot on about avoiding waste, and some have also used small ice cube trays before freezing and transferring, just to make sure each tiny feed is fresh and ready. On the Pampers front, I understand the cost is painful, Mamypoko is what most mums around here find most affordable for preemie sizes, though it might be worth asking your NICU nurses if they have any brand partnerships or samples, as some hospitals do stock a few options.
Your dedication to pumping while managing all this is truly admirable, but do have a chat with your lactation consultant or doctor about what works best for your body and baby's current needs, they'll know your situation best and can guide you through each stage. Sending lots of strength to you both.