Marrying on first visit is a very bad idea, especially when you got engaged before even meeting. The ideal situation would've been for you to meet him in person first, get engaged, leave for Canada to save up enough money for the wedding, then return to Nigeria and get married there, preferably with your family in attendance. This will cause your application to be minimally scrutinized.
But since you've already gotten engaged online before meeting, the next best thing to do to minimize the red flags, is to meet him for a month preferably, and spend time with him and his family. Get lots of pictures of you with his family, and his friends, you guys should be smiling, hugging, showing that you are happy together. When you return to Canada, by now you should have a good feeling as to whether or not he's husband material, should you now decide to get married, then you should start saving up $ for the wedding. It might be difficult since you're disabled, in that case, you can just have a simple ceremony with just close family and friends to save on cost. CIC should not scrutinize the simple ceremony because you should explain to them you are disabled, your husband doesn't make that much $ in Africa, so a simple ceremony is justified.
During the time you are in Canada, your parents and family should also start saving up $ to attend the wedding. They definitely should go, otherwise CIC will scrutinize your application because your parents and family didn't come. CIC won't accept excuses like your parents had to work, or it was too expensive, because there should be ample time from your departure from Nigeria, to the wedding date, so that your family can afford the tickets to go. If they can't attend, they must have a good excuse, such as very old age, no income, terminal illness, etc. The way they see it, your wedding is the most important day of their daughter's life, if they refuse to attend it, it must not mean very much to them. Bottom line, if you, at minimum, can get at least your parents to attend, that would do wonders for your PR application.
If they do come to Nigeria, get lots of pics of them with your husband and his family. CIC likes when they see both families trying to integrate with each other. Try to plan for a honeymoon, doesn't need to be in a fancy place or country. Save all hotel receipts, wedding receipts/deposits/invoices. Get lots of pics of the wedding ceremony/reception.
Just remember, it might seem like a good idea to quickly perform a marriage and do the PR paperwork, but it will actually cause you to wait longer, because you will likely get interview (causes about a year delay), then possibly a refusal + appeal (another year wait), etc. But if you just give it a little time and do things properly, you will possibly avoid the interview, thereby speeding up your application.
Good luck
