No Grace period. Marry citizen and have i-130 filed straight away [Getting good girl that are in GC/Citizen is hard, and even if you find them, they have so much pride on having that , they look down on you straight away, my experience ].

I am not sure about complications on going back to F-1 but if you have worked professionally for 5 years and have good IETLS score (or planning to give one), Canada is the best option. I have started my process for Canada as well.