Please help Dusty to get better

Well, here goes nothing. I don’t normally like to ask for help, and I have debated doing this for awhile, but again didn’t want to ask for help. I am now at my wits end and I will swallow my pride for Dusty. If you have ever met him you would know he truly is one of a kind.

In October my 6 year old dog Dusty came in from outside and I noticed that his one eye was swollen. At the time I thought that maybe he had gotten stung, so I gave him Benedryl and kept an eye on it. After a few days it really didn’t seem to be going down.
A few days after this I brought him to the vet and they did multiple tests and gave him an oral antibiotic which made him sick, so then we tried an injectible antibiotic which also did nothing.
After this, I took him back to the vet again hoping they somehow had another option for me, or maybe had time to think on it and could figure out what it was.After that visit I was sent home with Metacam( anti inflammatory) to try for a few weeks. The metacam seemed to be helping a bit, but not enough to know it was actually helping.
I made another vet appointment for him and this time they told me thwy were referring me to an ophthalmologist in Ottawa at Alta Vista Animal Hospital. $500 for just a consult , and they did the SAME testing that my vet did and still couldn’t figure out what was wrong with him, so they suggested doing a CT which was going to cost between $18-2400. That is a lot to swallow when the imaging still may not be able to determine what is wrong with him.
In April we ended up getting the CT done and we were told that there is definitely a mass , but the “fine needle aspirate” test they did determined that it was benign.
The ophthalmologist then recommended that we meet with the oncologist to discuss our options.

Finally a conclusion to this long post!!!
The suggestion that the ophthalmologist gave us was to remove the eye and the mass and some of his sinus bone because it is also affecting the bone. He thinks that the mass is malignant because it is continuing to grow in size ( even though benign masses can grow as well) but this procedure is going to cost us $3800. 
The reason I am asking for help with this is because we have just bought our first home, and as a lot of you know that is a very big financial stress all at once. 
I want to say thank you for reading my super long post , every bit helps.