I believe Bobcad had some kind of a gear tooth drawing function, it was not all that great, and required a bunch of trimming and perhaps redrawing the base of the tooth. Then, the tooth had to be copied and rotated to make a complete gear outline.
However, for working as you describe on a 4th axis, you might be better off to use a simple subroutine for each tooth profile, and then simply work out the number of repeats to equal the number of teeth in your gear.
You would first draw the tooth profile full scale, using, I guess, what Bobcad has to offer, which is only a standard involute profile. Then, offset the profile for half the thickness of the slitting saw. That would become your toolpath. It could be interpolated into tiny segments and translated into the proper YZ plane.
For one tooth at a time, I do not think it would be necessary to have the 4th axis performing live simultaneous motion. You can simply perform YZ interpolation along the path. Then, retract the tool out of the cut, and simply index the 4th to the next position.
Rather than use a slitting saw for tiny work, I think maybe an abrasive cutoff type wheel would be a better tool choice and these will cut pretty good in brass. You would run the slitting saw on a small dremel tool type spindle to get enough rpm to help retain cutoff wheel life.
For the purposes of simplication of the process, it might be good enough to assume that the shape of the edge of the cutoff wheel is a 180 degree radius, or perhaps you can dress it to that It will likely wear in to that pretty rapidly, I'm guessing.
It is important for the sake of running the offset toolpath, that the edge of the wheel be a 'hemispherical shape' so that the offset is a valid representation of the travelling center of the wheel's edge radius.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)