[EDIT]I (not completely, but mostly) agree with Robert Cartaino - while stats and quantity are good too, quality is more needed now. So I editted the post to emphasiye this.[/edit]
One thing to have in mind: statistics don't tell us much on the first day of private beta.
Questions per day: at the first two days, everyone is spamming the questions they had in mind when the site was in commitment phase. Having less than 50 questions on day one means that the site would probably never graduate, because it starts too slowly. This is an average for two weeks, so now the number is very high (74/1 is much better than few hundred/14), but the average at day 15 will tell the truth. I hope we will have 50 questions a day someday again, but it will happen long after graduation to full site.
On the other hand, quality matters too - 50 good questions is much more than 100 bad questions.
Answered percentage and answer ratio: this should be low during private beta. One of the purposes of private beta is to gather some momentum for the day it ends. If all questions had accepted answer at that moment, how would new experts willing to help join? If it looked like this in the end of april, it would be bad.
Number of avid users: you can't have really high rep users now - the 200 rep (except for association bonuses, acceptations and bounties) maximum wouldn't allow this. But ten "avid users" now is good, and more than half of the 206 users here is not bad.
Visits/day - we can't expect too much visits during private beta. This stat will reach its local maximum at the start of public beta, and then it will decrease and it will take hard work to merit its increase. It is a big holiday when the beta sites makes a new record in visits per day!
Just to compare, here are stats for sustainability.SE, a site that started more than a year ago, and now is not close to graduation, but not endangered by closing. I think we have slightly faster start than Sustainability (@EnergyNumbers might confirm or refute this, he has been much more active than me there since the very start of that site).
So what to do?
If you can ask more good questions, ask them.
We don't need to ask lame questions just to cheat the stats. We need to balance between quality and quantity. I remember fiasco of Machine Learning - they wanted to be really professional from the very start, but high percentage of the users (including me) wasn't able to meet the requirements for "quality" Q/A, so the site didn't survive private beta. On the other hand, Astronomy's private beta was prolonged due to low level. Moderate level is the key to good start; we can increase our level to "high" later. As I see it now, we are below the "moderate" level - so no need for overkills, but we should try harder.
The same goes for answers - don't be extra strict, but don't spam clutter. The risk of clutter is slightly more dangerous now.
The first two days we should produce a lot of questions, then ask more questions, but focus on good answers. No answer is better than bunch of bad answers on the release of public beta.
on day 8, the site should have some community, some style, and some 100-200 questions (the better questions, the less is enough); >50% should be answered with answers showing our style.
again, private beta is a time to find basic ideas. The earlier we find a style that suits the community, the better. At least if our style wouldn't be totally flawed (like "everyone go rep-whoring!").