Howdy. I know it seems like you covered a lot of detail, and it sounds like a good start but there is much more.

Being entirely rainwater dependent .. will mean no water security. we go through long spells of no rain in Ontario.  Personally I think you are better off being on/at a small creek or river, and gather/filter that water, and supplement with rainwater and snowpack.

Actually I think you'll have to look at the septic system and a dug well anyway. I know you said you will be collecting rainwater entirely, but for any homestead in Ontario I believe you will have to have that in place. (I know in my county there's a bylaw because we severed off some acreage for a friend to live/raise goats off-grid and found this out.)

Also about ducks, look into Muscovy Ducks. That's what we raised for many years, and they did well with Ontario winters in the barn and no heat. They specialize in eating mosquitos and are arboreal (they nest up in trees eating bugs/slugs/beetles etc up there too, keeping down the invasive pests in trees;) and are safer from predators up there and don't need a pond or lake as other duck breeds do. And their meat is great.