Not an expert, but I agree with Gliders. These baits do nothing on a constant retrieve, particularly a slow retrieve.
From an engineering point, the twitch or jerk sets up a single vortex, which sets up the lure moving in a particular direction. The next jerk moves the lure in the opposite direction, and so on.
The subsequent glide quality depends on the profile. A chubby lure will have poor glide qualities, a slick, torpedo profile will have a longer glide. it all depends on what you are looking for, and of course the definition; twitch bait, jerk bait or glider. Your bait profile I would say falls into the category of twitch or jerk.
Weight distribution is also very important. A central weight will cause the bait to over rotate in the XY axis, and the forward energy lost, thus killing the glide length. The weight should be evenly distributed along it's length, or at least front and rear, balanced for a level sink.
As for a rescue, I would say move on. Prototype and test before finishing. You cannot cut a lure and expect it to work first time without the experience. Your lure has not been a waste of time, as long as you learn from the experience.
As for determining the ballast, read the 'Archimede's dunk test' post. This will help you get closer to the suspender or slow sinker that you desire.
Dave