some questions about camera tracking

Hi folks, I tried the sinkhole tutorial from Andrew Price. But my camera only does a resolution of 640x480 and I can’t get a solving error below 1. What minimum resolution should my movie clip have? Or is it my fault that I don’t get a proper solving error? The clip provided by Andrew is no problem for me, the result was nice. Another thing are the keyframes. There are some tripod shoots in my clip but also some nice “forward moving” parts. Which amount of keyframes do you suggest? Minimum 30, max 80 or does it just depends on my clip? Some of my trackers are jumping around, would you delete them? If someone might have a look at my clip, here it is:
And here is a screenshot of my tracking marks:

Any help or hints is appreciated :slight_smile: