Three-Step Feeding Plan

My 29-weeker is now home from the NICU and is just two days shy of his due date. While at the NICU he learned how to breastfeed (sort of - thank goodness for nipple shields), but he only had a few days of breastfeeding practice before he was introduced to the bottle. After that I would usually try to BF 1-2 times a day and it was always followed by a bottle. We weighed him before and after each breastfeeding attempt and he usually only got 5-10ml even though he'd be working hard for 15 minutes.

Fast-forward 5 weeks. He has been home for a couple of weeks and I breastfeed him whenever he's in the mood (still usually twice daily). It seems like he has improved but when I saw a lactation consultant yesterday he still only took 8ml, even though the consultant said he was doing a great job and had good form. She said it would just take him time to gain enough strength to be able to extract more from breast. I asked her how many preemie moms she'd seen were able to breastfeed exclusively, and she said about 50%.

That number is not incredibly encouraging. Right now I am doing the "three-step plan" (attempting to breastfeed, following with a bottle, and then pumping). Right now this is more like a four-step plan because my son needs to be held upright for 20-30 minutes after feeding because he gets very gassy and uncomfortable. This pushes back my pumping, which makes me worry that the next time he attempts to breastfeed, he will get less milk and become frustrated. I'm afraid this will become an endless cycle. Also, the whole process takes an hour and a half at best (not including time spent cleaning pump parts and bottles). It does help save time when my husband gives our son his bottle.

I worry that all this is not sustainable long-term. I would love to be able to exclusively breastfeed but I'm a little skeptical it will work out. Do any of you have any experience with the three-step plan? Any support, advice, or experiences (good and bad) would be appreciated! Thank you!