Italian American marrying a Canadian

[Mars]

I was born in the States and now living in Rome (I have dual citzenship). To complicate my life I have a boyfriend in Toronto! I would like to move to Toronto and we have discussed getting married. The big question is my health. I have a blood disorder that require treatments every 3 weeks plus other check ups. Would this be a problem if we got married...in terms of applying for perment residency?
How long would it take? Because I need my treatments!
I want to think positive that my relationship will work out BUT if it does not and need seperation or divorce, how long before that can happen? Would I be thrown out of the country if we are not together anymore?
Thanks for your time!
Mars