1. Yes, you will get it at the land border. Probably will need marriage certificate and spouse's I797
2. Same day is also possible, but I would wait one night. Don't believe it would make much difference.
I have done both above multiple times.
@Rawhide - thank you for your reply! Good to know that we get H4 stamp at entry and no need to apply with consulate. We have already planned our move in a months time and I panicked when our moving company told us that we need to get visa prior to moving.
@Murthy2222 - were you able to figure this out? I am in similar situation where my minor child has Canadian Passport and I have H1B stamp. Trying to determine if I need to apply for visa stamp at consulate or we get H4 status in i94 as the road boarder.
How did it work out for?