Well it sounds like you know where this is heading. Any cancer left untreated daily gets progressively harder to treat and harder to get rid of completely. Days let alone weeks are important. ACC is very unforgiving of delays, and we know far less about treating it successfully than we do the more common versions of oral cancer like SCC.
ACC does not respond well to the tools that we use in other oral cancers, so that is something not working in your favor. It has a propensity to spread by peri-neural invasion, moving down the nerves to expand itself in to new areas. This is very hard to stop, certainly not as easy as heading off something that is in the lymph nodes and lymph drainage passageways. Rather than tell you the technicalities of ACC as we know them now (which is not fully understood) the bigger question at hand is getting his mindset changed. If he continues to live in denial and avoidance, then he is not going to survive this cancer. It's hard enough to beat ACC when people are actively trying, but without his cooperation to see a treatment facility, I'm at a loss of how to advise you.
Fear is the power behind avoidance. Whether he is putting on a strong appearance now or not, you have to know it is part of the underlying issue. It is totally normal to be afraid of something that has the potential to kill us. But putting your head in the sand only enables it, it does not move you to a place of overcoming the cancer or the fear. Perhaps he needs to talk to someone about his feelings right now, not necessary an oncologist, but someone that can get him to come to grips with his situation. You telling him that this is not just about him, but about the people he loves, and that while you are not the one that has the cancer you are the one that will lose something valuable in your life if he does not survive this, perhaps he will see a bigger picture of what the cancer will impact.
This will get worse even with treatments before it gets better. There will come a time when he can no longer live in the world the way he does today. It will slowly rob him of his life piece by piece. This is a long slow way to end your time on earth. It will reach a point that even if his desire to deal with it changes, it won't make any difference. I hate writing those words down here, but that is honestly where this will go. I and other are happy to talk to him and to you further, to try and turn this around. Fear does not always respond to reason, but attempting to reason with him and show him that the world is a better place with him in it, is worthy of trying. Please just let us know. B