Welle,
There is strictly no non-academic vocational student visa available for you. This is a shortcoming in US law. On the previous page of this thread you'll see where I have highlighted this problem which affects 'courses of study' having fewer hours than the minima required.
A B-visa, subject both to a clarified interpretation of the INA and to an amendment in US law summarised in the DOJ memorandum (linked by Gomrath), is not available to aliens entering the US to undertake a 'course of study.' The VWP is similarly inappropriate.
A pragmatic view must at some point be taken in spite of the minimum threshold on hours of studying per week required in part satisfaction of the M visa rules. In your position I would apply for an M visa anyway. The only sensible reason I can see for there being a minimum number of hours per week is to prevent aliens entering the US for prolonged periods, notionally studying, but in reality engaging in labour.
Best of luck.