You don't have to necessarily join all of your accounts. What USCIS considers is the quality of what you have joined together and, in general, what other proofs you have of your life together. A joint bank account is great, but, what if you hardly ever deposit money into that account? Quality over quantity is a good rule to follow when preparing your proofs. Good luck.
1. Yes, this is primarily accomplished by showing that the Citizen will be starting a job in the U.S. or something long-term of that nature.
2. It's true that one cannot have immigrant intent while on the B1/B2. However, entering for temporary purposes and then deciding to pursue the green card later is a different matter.
I suggest a consultation with an immigration attorney to flesh out all of your options. Good luck!
In VA, you may have grounds for a Padilla-based habeas writ since the conviction occurred within the past 2 years. If your attorney didn't know about your non-citizen status and/or gave you incorrect advice regarding the conviction's effect, the claim will be stronger.
You will likely be interviewed in Norfolk, VA, where the processing times are rather fast! If interviewed prior to your 3-year green card mark, it can delay the entire process. I'd be happy to discuss this with you further.
You should file for Naturalization. In Northern VA, it takes approximately 2 1/2 to 3 months for the interview. Then, you can get married and file for her green card. She'll have to spend quite a bit of time in the U.S. after getting her green card, so that may put your quest for Canadian status on hold for a while.
He may be subject to "reinstatement of removal":
INA § 241(a)(5) - “if the Attorney General finds that an alien has reentered the United States illegally after having been removed or having departed voluntarily, under an order of removal, the prior order of removal is reinstated from its original date and is not subject to being reopened or reviewed, the alien is not eligible and may not apply for any relief under this chapter, and the alien shall be removed under the prior order at any time...
Keep in mind that, since you didn't list either offense on your green card application, the officer may ask why not. With that said, err on the safe side and bring a certified court disposition (if it exists) and proof that the fines were paid to the interview. If these are considered more traffic than criminal infractions in NY and the fine is less than $500 (as you mentioned), neither should be a problem for naturalization. Consult with an immigration attorney who has knowledge of NY...