I hope Theodore is hanging in there! I’m going through a similar experience myself 
Mr. Bun Bun hasn’t been eating normally for almost a week. I took him into the vet as soon as I realized it, and they didn’t make it seem like I needed to leave him there. And it was expensive so I took him home. They gave me SubQ fluids and critical care (along with a couple of other medications). I thought I was doing okay with it for the first few days, and he even ate a good amount of greens on Thursday night. But on Friday he was giving me such a fight. I had a follow up appointment on Saturday and decided to leave him there. He’s been there for over 48 hours. Today the vet said that he is eating more now but still hasn’t pooped. I think the last time he pooped was just a little bit on Thursday night/Friday morning.
I’m really worried about him because I didn’t even know this was a common problem in rabbits until now. I hope it didn’t take me too long to realize that something was wrong! Hoping to hear back from the vet within the next few hours.