A 2-7X or 1-4X on the low powers is just as fast as a red dot up close without the downsides. The 2-7X Redfield is a good choice. This would work well enough to 60 yards and is around 8 oz. http://swfa.com/Leupold-1-4x20-VX-1-...pe-P51851.aspx
if you are trying to go light. No reason to spend much more for the recoil and ranges you will be shooting with a rimfire.
If you really want a red dot, consider a conventional scope with an illuminated reticle. http://swfa.com/Leupold-125-4x20-VX-...pe-P48030.aspx
More than I'd pay, and a bit over your $400 budget, but a good scope.
I understand that typically subsonic ammo is the most accurate? Is that true?
Usually, but not always. My CZ shoots subsonic target ammo more accurately, but my Ruger 10-22's like the CCI Mini-mags better. At least better than the Wolf or Ely ammo that I shoot through the CZ. You'll just have to experiment with your rifle.