My experience of getting the DTV is they are more concerned about being able to show the 500k thb requirement than the reason for getting it. Also i had to apply using the evisa system; basically if you don't have all the right docs they don't refuse straight away instead telling you what is missing and giving you time to submit all the right docs. Thus if they are not happy with the docs for the course, etc, you can try another course, etc.

You can't take land with you when you die. With this mindset do you need to own it? Rent is the cheap answer; when you are fed up with it you can move on.

Just close the door and forget about. Not worth getting all stressed and wound up by a small thing like this. One thing i learnt from experience: it takes a lifetime to be wise.

Correct. You can go late up to 7 days after or 14 days before. You can do the first report by post as long as it arrives before your due date. Since you report to the local provence immigration send by post should not take more than 3 days. Offical docs: