1. Your trip is business because the main purpose is to get business training. If you tell your purpose to the consulate the true reason of your trip, I don't think you can get a visitor visa.
Business visa is more flexible. You cannot work during yur tourist visa, but you can sightsee while on work visa.
2. Multiple entry visa would be difficult under business visa, since your work trip is one-off, there is no ongoing need to travel to germany. Unless you can have someone write a letter saying you will go backk pretty often.
3. medical insurance by schegen country, you can simply do a google.
4. You can purchase a refundable full price airline tickets, and then cancel it afterwards. Trust me, airline will refund it. Itinerary can be just based on letter/email by your german host.
