I had golden oak cabinets in my kitchen and used Annie Sloane Chalk Paint on them. I was inspired by some really nice looking projects on this site using ASCP. I have attached pics of the before and after. ASCP was developed in the UK, I believe, so I assume it is less toxic than oil-based choices. It certainly did not stink up the house. In my last house, I did the whole sand, prime, and then paint with oil-based paint on my kitchen cabinets (dark oak to white), and I found that to be a lot more work than using ASCP on my current kitchen. As you noted, painting kitchen cabinets is never easy, but comparatively speaking, I liked this method better than sand/prime/paint.

I've read good things about Rustoleum Transformations and they are available in Canada: http://cabinets.rustoleumtransformations.ca/

Fine paints of europe brushing putty or Swedish putty.

This is a big job. I'd be looking at new paint grade doors before trying to fill the grain.

I also don't see a problem with the oak grain showing.