help with feeding issues please!

needing some feeding advice from other moms..... I have a 4 week old baby that was born at 35 weeks... He was in the nicu for 14 days with small issues regarding jaundice, weight loss and learning to eat, and bradycardia during meals... We eventually got him up to about 60-70 ml and got everything else under control and were sent home.... the first week was great, he was still on his NICU feeding schedule of roughly 2oz every 4 hours. he gets neosure 3x and pumped breastmilk in a bottle 3x a day. (I have a HUGE supply and the letdown was too strong for him, even if I pumped first, it was so bad it caused him to choke and his heart rate to drop into the 50's so we stopped breastfeeding and just gave him breastmilk by bottle)... his feedings took over an hour most of the time and he seemed gassy so I switched him to Dr Brown's bottles, they helped a lot, most feedings are now at max 20 minutes.... then we started to notice he would wake up 2 hours after a meal acting hungry, you could even hear his little belly growling! so just as a "snack" I would put him on the breast for about 10 minutes. He seemed to handle it well this time but it was exhausting for both of us to be up every 2 hours.... it was suggested to offer him 3oz with his regular 4 hour meals and see if that held him over bettter... He downed every bit of it and slept the whole time between meals! it seemed great for a day or so then he started to act like his belly hurt so I backed it off to 2.5 oz. thinking it may be too much for him.... He still did well and didn't need his "snack" between meals.... but at his last feeding we had some issues.... He started out great as usual, then after the first ounce he started getting fussy and arching his back like he does when he needs to burp, so I sat him up and he burped immediately. no patting required... 2 seconds later everything he had just ate was spit up and running down my arm.... i figured it happens and kept going, he got another ounce down and did the same thing, burp followed immediately by spit up... Less this time but still.... the last half ounce he fought to take, he still acted hungry but after a few sucks on the bottle he would make this miserable face, start fussing and spit it out.... so I put him on my chest for about ten minutes and he would not sit still... moving his legs, curling up and arching, just general belly ache type symptoms.... so I gave him some gas drops to see if they would help... He spit up again..... He has spit up twice since birth, this is not like him... He did calm down some after that and has been sleeping in his swing (I didn't want him flat on his back with him spitting up like this)... but we are now at the 2 hour mark and he is starting to fuss like he is hungry again... I know he didn't keep down his last meal so I expected this but does anyone have any suggestions going forward? I hate to see him miserable and if more frequent feedings are need I get that but after a while of feeding every 2 hours he was too tired to even try... struggling to find a happy medium here....