chicinchic

I am Canadian.
Why go on the trip? Because it was literally the only week in the upcoming years when we could. Keep in mind that I thought that we had been cleared for the trip; I had mentioned the trip as my basis for parole, and when I called USCIS, I had been told that the interview would be scheduled. I took whatever precautions I could, and acted accordingly.

It takes 60-90 days for an i131 to get approved, and this is provided you do not run into delays due to RFE's. Thus applying in February for a trip in March may be difficult.
You can apply after your trip.
If you are married to a US citizen, having your J1 status expire should not be an issue. As you are aware, Canadians are not issued a Visa, rather they are given status (J1 in your case) upon entry with a DS2019.

I would file before you leave and then make an INFOpass appointment to see if you can get AP before your conference. If you have no travel documents before the conference, I would not attend or when returning to the US I would mention the AOS and see if the CBP officer will allow you to enter based on a LPR and not a Canadian with J-1 status. If not, you will then need a spousal visa in order to legally immigrant to the US. To leave affer your marriage and return using the J-1 and then filing for AOS is visa fraud as you would be using a non-immigrant visa to enter the US with the sole intent of filing for AOS so you can remain in the US.
As a Canadian you have it better than most as you can come and go almost at will. This does mean you need to be more careful when you decide to immigrate to the US so you are not committing fraud.
Good luck,
Dave