in the 'stats' tab, in the long run, the "site is up" value should approach the value for "wagered" times the house take of 1%?
Right now that would be about 30,256BTC * .01 -> 302.56BTC.
Also, is there a way now (or a way planned) to track the history of the values in the 'stats' tab in an automated way?
That's right. "house is up" should be 1% of amount wagered, and is currently only a little over half of that.
There's no history of those stats available yet, but in time I will provide API access to the history as well as charts on the site.