Are you able to do sleep shifts with a partner ? Often means going to bed very early in the night but a few hours here and there really helps.
Sleep deprivation is tough. As someone that loves a good sleep, I found it really hard. My LO had reflux and colic too. We have a cot that can lift higher on one end so he sleeps at a slight slant. We also made sure he burped after each feed, or even a burp during the feed (if he allowed it). Keep him upright or slant your body when sitting so they can fall asleep. We transferred him to his cot sometimes 30 mins after he fell asleep. Sometimes it’s the heat and smell they need, so warm the cot in advance ( hot water bottle) and leave a worn top with their blanket. In terms of getting sleep myself, it’s tough sometimes, it does get better for sure. I watch videos of him when he was smaller and remind myself why I am awake. Otherwise you can try napping when they nap ( co-sleep). Hope some of this is useful
LC