Your understanding of RPM is correct. From their help document:
Page revenue per thousand impressions (RPM) is calculated by dividing your estimated earnings by the number of page views you received, then multiplying by 1000.
Page RPM = (Estimated earnings / Number of page views) * 1000
For example, if you earned an estimated $0.15 from 25 page views, then your page RPM would equal ($0.15 / 25) * 1000, or $6.00.
To make $100 you would need varying numbers of pageviews for different RPMs:
RPM Pageviews to make $100
A $2 RPM sounds quite typical to me. By optimizing your ads (experimenting with color, layout, and prominence) you may be able to increase that to $4 or $5. RPM also fluctuates seasonally. Advertisers are willing to pay more at different times of the year and as their ad budgets allow.
Google Adsense only displays estimated earnings until the end of the month. After the end of the month Google will "finalize" any earnings. That process will likely reduce the estimated earnings somewhat by taking out any invalid clicks or clicks for which Google didn't get paid by the advertiser. If you meet the minimum payment threshold and have entered all the documentation needed to get paid, you should get the money at the end that month. Finalized earnings appear directly on the front page when you log into AdSense: