From what we could find, Tomodachi Life: Living the Dream will not have polyamorous relationships.

According to the demo files, Tomodachi Life: Living the Dream currently has 196 foods out of 465 available across all regions.

We can safely confirm there is a limit of 70 Miis in Tomodachi Life: Living the Dream, according to the demo files. If this measure changes upon release, we'll update you as soon as possible.