I'm pretty sure but Kazuma doesn't wear a lab coat. He specializes in Sky Dragons but that doesn't mean he wears a labcoat. I think he just has a dress shirt thats untucked. Thoughts?
1.A lab coat that ended just above the knees would probably look best - he looks awkward without some sort of coat.
2.Yeah, if you ask everyone about every little detail then the comic won't be quite as much yours - not to mention eventually people will get annoyed at being asked everything when all they want to do is read an entertaining comic about Cave Story.