I'm so sorry that this is happening to you and your spouse. This is not your fault. I suggest contacting the Alzheimer society to see if they have any ideas about how to get some assessed. I imagine most people with early Alzheimer are not willing to see a doctor about it, so I'll bet they have some ideas for you. Here is the web page for the branch in Sidney. http://www.alzheimerbc.org/In-My-Commun ... sland.aspx
You're right that increased irritability and personality changes are a big concern for your partner's brain health. I suggest keeping a log of what happens to help with diagnosis, but that alone is enough to warrant a doctor visit. You might also be able to get your local mental health team to come and do an assessment. Since he has good days and bad days, if you can find a pattern in when he is likely to be not having a good day (Alzheimer is sometimes worse later in the day for example) it might be good to let the team know that. Here is the intake number for the mental health team in Sidney: (250) 519-3485 (and more info here: http://find.healthlinkbc.ca/search.aspx?d=SL076587
) You can call them, explain that your spouse has had severe personality changes, increased irritability and rage, has assaulted you and you are afraid for his health and your safety, and ask that they come and do an assessment. Be sure to tell them that he has good days and bad days, in case they come on a day he is well.
You deserve to live in a home free from violence, no matter what is causing it or whether he can help it, and shouldn't have to be walking on eggshells. You still have that right whether your partner agrees or not. You also have the right to call the police if you are feeling a threat of violence. Throwing a plate at you counts legally as assault. If your relationship is harmful to your health now, you have a right to put yourself first and protect yourself. You are not the first person on this list with an ill loved one who has had to make a choice when faced with an ill relative and violence. It's a hard thing to have to do, but if your partner was well I am guessing he'd want you to be safe too.
I know it's hard to make big changes without support. I will do whatever I can to hook you up with services that can help you. I'm including in this post what I can think of right now, and please feel free to ask any questions. I'm good at finding services for people, and if you get any attitude about being in a same-sex relationship, or being a man experiencing violence at home from any of the services, let me know and I'll find someone to go to bat for you.
Just in case you're not aware, the laws around same-sex couples have modernized, so if you two are not married, you are definitely common law spouses, and if you decide it is necessary to separate your legal status is almost identical to that of a married couple. This means if you split up, you have a right to half of your joint assets and all the things straight people get. I'm not a lawyer of course, but that's what I've been told and I believe it to be accurate.
If you feel like you are sitting on a time bomb, you need to trust that feeling. I suggest making a safety plan for yourself, making sure you are aware of your joint finances, have some separate money put aside, and have what you need to can leave quickly if things in your home feel unsafe. You might also contact a friend and arrange for a place to stay with them if you need to leave late at night in an emergency.
I'm not sure if your finances are separate enough that you can get legal advice easily without consequences. If that's the case you might find this program for seniors (yes 56 counts for this program) which is intended to help in situations where an older person is experiencing violence in their home might be able to help you and give you some legal advice: http://bcceas.ca/