1) Ok, I will wait until H1 approval and then apply for Nexus card.
2) Yes, I softlanded on Aug 30, 2017 in Saskatoon. Great to meet another SK nominee
3) You are right. But just like you mentioned, I don't want unnecessary issues. I am thinking you are working at Detroit office? So it would be enough to have a place in Canada for you and give that address for H1B also. But I will be "working from home" in WA/NY. So I will have to provide that work location address for H1 amendment, hence will have to have an address on US side. Actually, I am doubtful of the fact that because I will not be working at an office in US, would that be a problem whenever I cross the border?