If you can't find the answer on the CIC website, you can have your spouse call them and ask. To qualify for common law, you need to have lived together for at least 12 months but if you are not living together anymore as I assume you are not since you are residing outside Canada and spouse must be living inside Canada to be able to apply for citizenship, I do not know how much time apart would be considered not to be common law anymore. If you get married, you have no problems.
You can do sponsorship without using a visit visa if you wait where you are until sponsorship has already gone through.