Hi Mike,
1. We have included all the times we have lived together and it was also very sporadic. A few months here and a few months there. There is an option of providing additional detail on your application on separate sheets of paper, and this is where we explained everything that we thought might have been confusing or required additional info.
2. I was going to change jobs a month after we have filed our application, and I have included it in the file. Since I knew all the details, I reasoned it would just save me the hassle of updating the info later. And I explained it further on those additional info pages.
3. You send the entire package to Mississauga, and they will forward everything to Buffalo. In fact, they go over the entire application, making sure everything is filled out correctly, and if it is not, they will send part or all of it back, which can delay you by a few months.