You could do an insert mate for aligning the elbow with the pipe. You can do an align/mate with an offset fromt he edge of the elbow to the edge of the pipe (for how much the part will be inserted). Make sure that allow assumptions is off. Finally, I would change from placement to move tab (and motion type to rotate) and rotate the elbow more than 90 away from where it needs to be. Go back to placement and mate the plane of the elbow to the plane of the pipe and it should give you a orientation (in degrees) that you can set or tweek to get the correct alignment for the elbow.