Afaik once your priority date reaches the final decision state, you have an year to find an employer and apply for a green card via consular processing.
You can’t have them file a i-485 while you’re in Canada as the 485 is a change of status and you need valid status in America for that to happen.
Another option is to find an employer who will file a H1B cap exempt petition for you, to then move back to America and then file a I-485.
If however you’re not able to file for a green card within an year of your priority date becoming current, then you will forefeit your priority date and have to start everything afresh.
So if your intention is indeed to settle in America or to get a green card, you should move fast to find an employer who is willing to sponsor you for an employment based green card. I think the current final action dates are for 2011 and COVID has really helped move the green card queue for people of Indian birth much faster than it had moved in years.