I just thought I'd throw this in here, in case you haven't see it yet. Sorry if you've already mentioned it...
Bob Warfield has apparently been doing a series of articles on building the ultimate benchtop CNC mill. Maybe there's some tips in there that would help you out. Here's part 7 (there are links to the other six parts on that page)...
Ultimate Benchtop CNC Mini Mill Part 7: Spindle, Drawbar, and Toolchanger - CNCCookbook CNC Blog CNCCookbook CNC Blog
... later ...
Having now skimmed the articles, I think it looks like you've already surpassed all the topics covered. Well, maybe it's still worth a read.