Help with Sony Vegas

I've created multiple layers with different keyframe lengths. Is there anyway to loop them without having the shorter layers disappearing half way through the loop, and have them continuously loop with the longer layers?

Simply set them to the self length.

Whenever I try to resize an image with a tween motion (using lock), the tween motion changes its original course. Is there anyway to prevent this?

If the first and the last frame of a tween have the same size, there shouldn't be a problem.