I'm so sorry to read about your mom and the helpless feelings you are going through. I'm glad you reached out here to us, because even if just one stranger on the internet can give you some hope or confort that may help you get through one more day.
Ok here's my two cents. I see a lot of potential to make this work. Since the time it will take for you to get to the point where you have to show proof of income or assets is a long way off. Not to worry about that right now, take care of your mother.
I would forget about getting married in Ontario, they are notoriously slow getting the marriage certificates back. That would just add more time to your waiting. Since you have known your fiance for years and just reconnected. Go and visit and get a good feel of it all and then you can get married via Utah marriage it's online. It would be much faster then waiting for Ontario to send you your marriage certificate. If you can visit earlier then get married earlier. Also make sure you two meet after the Utah marriage if you go this route and are not together when you get married. If you get married via Utah marriage while you're together then you can file right away.
You are one strong women, do not ever forget that. You can do this.