Bezier paths can not be broken into two nor can two of them be joined into one in Strata. You can add to an existing path however by selecting the original path then choosing the Pen Tool and clicking on one of the end points to continue drawing from there.
Strata assigns an equal amount of time between each Bezier control point when the path is made into an animation path with the Convert to Path Tool so if the points are not equally spaced along the path the object will change speed as it moves along. The speed between closer together points will be slower than the speed between points further apart.
You have some degreed of control over the speed between each point by double-clicking on the control point to open the Event Options dialog. In the upper half of the dialog are Velocity controls where you can set the acceleration as the object approaches and leaves the point. The only real way to do it though is to adjust the Keyframes so the speed of the object remains constant. Move Keyframes for close together control points closer together and move them further apart for those Keyframes which are further apart along the path.
You know I was just thinking, Although it would be good to have better path tools for this kind of thing, perhaps something like smart objects in Strata would be helpful. I mean a relational approach where the path editing (joining etc.) could be done in Illustrator then Strata would recognize this and reflect the change! Strata does this now with textures!