Very sorry he is going through this war. First and foremost he must avoid becoming a victim. What I mean is remain perceiving himself as a normal productive person who has a problem that needs periodic attention. Stay strong and defiant. Do not tlet the beast control his life. Encourage optimism even though in the middle of an attack things seem helpless. It is not a helpless situation. He needs to take cantrol and educate himself on available treatments and then partner with a provider to get access to the resources needed to do battle.
First and most important get the correct diagnosis. Cluster headach diagnosis can usually be made on history alone and the absence of other findings. Most folks nowadays get an MRI or CT scan but they are almost always negative. If the doctor is equivocal on the diagnosis get another opinion. Avoid a "lets see if this works first" approach
If you get a cluster headache diagnosis get the Oxygen right away: Presciption for high flow O2 at 12-15 LPM with a non rebreather mask to start. If your doctor doesn't want to prescribe or waste your time with other things first; get another doctor who reads and stays up to date. There is not a single credible source in the medical literature that doesnt suggest O2 therapy as a primary abortive.
Have him read about the D3 regimen and start it. Follow the protocol to the letter. I'd link it for you but I dont know how. Someone will. Imitrex injections may be offered and do work but try and cut the dose in half or a third. Nasal has some effectiveness but not like a subq injection. Pills are worthless to abort.. Imitrex is a two edged sword and best to avoid is possible; sometimes it is not possible so don't feel bad if it comes to that. Prednisone will help kill a cycle but must be used aggressively and there are side effects. Same for Verapamil, depakote and lithium.
There is no new information in what I have written here. This site is well organized and accessible. There are many members with lots of experience and wisdom. It is a strong tight community. Read the pinned info and take notes. Go through treatment options systematically and consider busting alternatives only after careful research, self education and proper reflection. Busting can be a godsend but it doesn't work for everyone and everyone doesnt have to bust.
It is good your son has strong family support and he is lucky you love him so much. Help him direct his own treatment and encourage him to live normally with the beast doing battle at times. Encourage him to educate himself and participate in his care. Discourage him from becoming a victim. He might lose a few battles but he has the resources, like this site, to win the war.
Good luck