Also, notice the link between document dpi and 72dpi, which I now think cannot be coincidental.
My document at 300dpi, a 12pt font becomes 2.88pt
Your document at 150dpi, a 12pt font becomes 5.76pt
300dpi / 72dpi = 4.166...
12pt / 4.166 = 2.88
150dpi / 72dpi = 2.0833...
12pt / 2.0833 = 5.76