Yep, you did it right: 900 GB/month in KB/sec. Of course it depends on how long your "month" is (30 days or 365/12).

If neutrinos were the missing mass, wouldn't we be detecting far more of them? Either the mass would be big enough to have shown up earlier, or the sheer number necessary to account for the missing 90% of matter would make them more likely to hit our detectors.

I thought that the current theories of the big bang set a limit on how many neutrinos would have been produced. If there were lots more neutrinos then the ratio of hydrogen to helium would be different, something like that.

This is clearly not my area of expertise, but perhaps there is someone out there who can make a more coherent statement of the problem?