In the face of increasing tensions over the Russia probe the Russian Candidate will be looking for ways to divert attention from it when he gets back from his road trip. 

He could try for a quick NAFTA deal concurrent with the end of the probe so that it masked the probe findings. His supporters in Congress can probably delay the probe timings to suit this scenario. From what I read there are only a couple serious trade irritants. (softwood lumber is not amongst then since it is not covered by NAFTA). There rest of US concerns are more of a regulatory nature that could be covered by side agreements.

On the other hand he could try for a lot of chaos by demanding extreme changes to NAFTA knowing full will that Canada and Mexico would not agree, opting out before talks start and ratcheting up rhetoric at home. That would play well to his supporters, keeping the impeachment process at bay while the probe is slowly forgotten.