Oh my goodness he is so adorable. He is about the same size as my girl Karma, who was about 1.8 at 8 weeks. Now at 12 weeks, she is almost 3 pounds, and expected to be about 6 at adult weight, according to something that I read saying to double the 12 week weight to get their adult weight. We were told Boomer was a teacup too, without knowing that there is no such thing, and if there was, they are just more susceptible to problems...
Good luck with him, and just wait until he REALLY gets going
Love from Karma and Boomer