No. That's the application fee. (Or something close to that depending on where you apply). You'll have an extension cost of 1900 baht and a border bounce/crossing to do every year for five years.
You can still get a five year multiple entry visa. I visited a cooking school yesterday, paid for classes, got the paperwork needed for the DTV and will be applying in Laos on September 10th. The cooking school I used here in Bangkok said they already had four other students get the DTV with their classes.
Once here you can get a new passport at your embassy (if you have one in Thailand) then transfer the visa and respective stamps to the new passport. It's a standard process here. The visa is five years in length.
You are right. There is no requirement regarding the duration. It could be one day or 20 days. However, the course itself needs to be accredited by the Ministry of Education, not just the school. Many of the small cooking classes tourists see online are not actually schools but glorified tourist attractions.