Duration of courses: hours to weeks and self-study time
Regarding your first question for a "common conversion":

In Germany, workload for a course is measured in "hours per week in a semester" (abbr. "SWS" for Semesterwochenstunden), which would be what you are looking for. For singular events without a weekly schedule or for events where you need to calculate from a fixed number of hours, you can use the average (14 weeks / semester) or the real (12w / summer semester, 16w / winter semester [in Germany]) number of weeks and if needed the "academic hour" (which officially lasts only 45 minutes here) to calculate back.

As an example: A short practical course in the winter semester goes over 4 days with a daily workload of 6 full hours (breaks etc. already substracted).
This corresponds to 6 * 4 / 0.75 = 32 academic hours. As the semester has 16 weeks, the 32 hours correspond to 2 "SWS" or hours/week.

Formula: full hours [/ 0.75 if needed] / #weeks = hours per week

Covering your second question: 

If your current university includes "self-study" time in the total course time, I would also stick to that in calculating the final "hours/week" for the course. Although it might be confusing if some course include self-study in the total course time and others don't, you should not alter the official course time given by your university.