Rescued bunny w/o incisors

[mizunodaddy]

Hi everybun!
So, i got this bunny from rescue. He has no incisors, but one pair (upper+lower) is starting to go out and our vet told me his front teeth are not likely to be malformed. In the meantime he has this persistent eye inflammation thing: conjunctivitis and weepy eye... He underwent an antibiotic 8 days' course (metronidazole), and is now on painkiller (without it he stops eating and becomes lethargic) and i now am using the prescribed eye drops (neomicin) which is like rain to this inflammation. However, his right eye is now normal (since the antibiotic course), the left one is in the same inflamed state. I understand that the main reason is weakened immunity system. I gave him a suspension of pulverized mix of herbs - echinacea, dandelion, ribwort - for several days but he would accept it with so much fight that for now i paused these efforts to spare his nervous system.
The bunny was found in a closed cage on the streets sitting in his piss and feces for hours or days, allegedly having broken his teeth when trying to escape. Initially he was addicted to a garbage-grade sort of pellets and didn't accept any other foods even greens. I managed to switch him over to the best pellets i found on the market, four varieties, with vitamins with minimum chemical additives. He is still indifferent to hay, but occasionally, due to time spent with my original bunny (my "biological" bunny) who has normal diet (90% hays+herbs, 10% green leaves) he started trying new things and he sometimes eats ribwort and dandelion leaves.
I am asking for any info or advise from those bunparents who had experience solving similar problems.
I have these questions:
1. Is there any way to improve bunny's immune system? Any other info related to the above is appreciated!
2. How to stop this new bunny from pissing his way through his new life! he is marking everything everywhere, pissing on my original bunny's stuff! A notorious and dedicated pisser her is! Is it temporary? He was neutered but it ddn't seem to matter...
Thank you everybun, have a bunniful weekend!
On the picture: bunny Haru - image taken by a rescue team member

 

[JBun]

I hope you were able to find some answers that you needed. But here's some additional info in case you still need it.

A rabbit consistently urine marking, I would suspect they weren't actually neutered, have a medical issue like a UTI, a litter box and/or area set up that isn't working out for them, there are other rabbits or pets around that the rabbit feels a need to mark their territory, or the rabbit is traumatized or very nervous and having urinary issues as a result.

The immune system, I've read of owners supplementing with echinacea, but it's not something I ever tried. So if interested, make sure to properly research it.