1. Everybody who moves to Ontario has to go through the waiting period.
2. and 3. You should talk to OHIP about this. You can find them at http://www.health.gov.on.ca/en/public/programs/ohip/
Nobody else can really assure you that you will be covered.
Even if you had OHIP, depending on how long you leave for, you can lose it again if they know you were gone. I believe it's 6 months you can be outside Canada until they consider you not living in Ontario anymore but do ask them.
If you want to move to another province like AB and I believe SK, they will cover you from day one. Some provinces, I believe Quebec make exceptions to the waiting period for pregnancy and delivery.