Cat with Calici - vitamin supplements?

I've made a few threads about my kitty cat Nacho and his Calicivirus - and I'm looking for some supplements I could give him!

I've got him on L-Lysine right now, but I've been unable to trick him into having it in treats in the morning so he's only been having 1000mg in his dinner. I've bought a pill popper from ebay so I can give it to him that way! Then I feel it'll actually be more effective.

His symptoms are bad gingivitis, death breath, gunky eyes and - uncommonly - runny nose. He doesn't sneeze much if at all, and drinks plenty of water and has dry food in the morning and wet food at night. His diet is completely grain free. 

I'm looking for anything I can give him to improve his overall mouth/everything health in the meantime before I can start any other treatments for him (due to funds, unfortunately - I am in debt almost $1,000 from vet bills already!!). I was given some antibacterial oral gel, and some "mouthwash" for his water, but these things didn't help much if at all. 

I heard Evening Primrose oil is good but he doesn't have any issues with dry skin or anything, unless it helps with other things.

(I'm located in Australia so hopefully I have the same stuff available as in the US!)

Thank you very much! Here's some pictures of my little goofball to make this less text-heavy:

I don't know about the specific problems Nacho is having, but I also have a calici-infected buddy. His symptoms are totally different, though. Sometimes (but rarely) gunky eyes, and LOTS of sneezing, stuffy nose.

I give him L-Lysine, too, but I got the powder. He doesn't even know he's getting it. I mix it into all of the cats' water, and also into wet food at night. So, just a thought--maybe you don't need the pills.