Hi,
You will likely get more answers if you post questions in the Design and Documentation forum. Regarding sketch geometry moving like that when the sketch is redefined, this can be prevented by fully defining/locking down the sketch geometry. Ways to do this I know of include dimensioning with the Dimension tool enough of the geometry with respect to the origin, or with respect to a projected (purple) feature from another sketch or other feature. You can also fix (make green) enough of the sketch geometry, under the constraints tools in the sketch window, that should hold it down.
If you need more help let me know.
Jesse
