Might be stupid remark (sorry if it is
), but regarding your point 3. are you sure the nylon locknut of the pedal pivot is not too tight, which would explain the slow return? Loose the nut until you get a play, and tighten it just until the play disappears, not more.
I had a quick check on Internet, and I found this forum. The guys have the same problem as yours, and one of them publish pictures of his solution. I think using a car throttle cable is actually a good idea. Then he welded some bits to fit it, as well as a pedal stop bolt.
http://bbs.22b.com/forums/showthread...-Obp-pedal-box
Hope this will help
