Hi there! Congrats on getting married! I wouldnt waste your money on an immigration lawyer if your case isnt very complicated. You can get a lot of help here!
Yes, you can visit him in Canada for upto 6 months. If he can get his child support out of arrears by then, and you send in your application for PR and have the receipts for it, you can extend your visit by sending in $75 along with the proper paper work by your 5th month of visiting, requesting to extend your stay so you can continue visiting your husband while your PR is in process (and submit all the proof you can that it is processing, such as the receipts for sponsorship and PR app, and if you have it already - your sponsorship approval , along with your birth certificate, and a letter from your husband along with proof of his income that he will be financially supporting you while you are visiting. It takes a few months to get the approval back (as of right now), but during that waiting time you are on implied status, and you can continue visiting until you get a decision back.
And yes, you can file outland through Buffalo while you are visiting him in Canada. We are doing that right now - my spouse has been here for over 19 months now on an extended visitor visa.
Just when you cross to visit him, make sure you dont say you are living with him for 6 months, make it clear that you know its strictly a visit.