Update: Rambo's eye was doing well this weekend, and I had high hopes that we were on the right track. When I came home on Sunday he had a bit of discharge from his eye, so I cleaned that up and not 30 minutes later his eye had swollen up till you couldn't see the eye anymore. He was going crazy with it so I gave him something to make him sleepy in the hopes that he would leave it alone for a bit. (vet was on the phone with me during this!). Then I tried (and struggled like crazy) to get a dose of antihistamine in him. This morning both eyes are kind of swollen, and one is weeping. His coughing has started up again and I'm waiting to see if the blisters reappear.
I contacted 2 pharmacies about compounding and they didn't have anything to offer. They said they could do it, but most of their bases (liquid) included sugar. I'm going to try a trick my rescue director offered to hide it inside a yogurt and cream mixture in the hopes of diguising the taste. We're still not even sure if it's allergies, and if it is....what is he allergic to that stopped for 4 weeks and then came back.
Thank you all for your suggestions and insights. My vet was very interested in what you guys had to say (as she didn't get any replies on a vet forum she posted on about Rambo).
Please continue with the prayers, and healing vibes. My poor baby is so miserable, and hates me at the moment.