MSV Duisburg will surely extend the gap to 8 points with a win against Carl Zeiss Jena tonight, though.
I think that the U-23 sides are not eligible for promotion to Bundesliga 2 - that was certainly the original plan, but who knows?
TSV are no longer allowed to share Bayern's stadium, though I believe Bayern ll still play at TSV's much smaller ground.
I think moving back a couple of years ago was a popular move with most of the fanbase.