you can set a frameDuration(seconds) for every frame. This will speed up if you keep the same amount of frames.
If you want to keep the same length of the animation you you have to use a combo of a higher frameDuration and a higher frame rate.
see http://www.drawbot.com/content/canvas/pages.html#drawBot.frameDuration
The documentation is adjusted and path.onCurvePoints and path.offCurvePoints and the path contours are immutable now.
The attributes onCurvePoints of a bezierPath is a immutable representation of the path points.
I would like to encourage you to look at pens and how to alter point data and point structures while drawing in a pen.
see
A drawBot BezierPath is also a pen.
continue here: https://github.com/typemytype/drawbot/issues/347
I only wanted to teach you how to narrow down the problem, by elimenating parts :), make the problem as small as possible and fix the smallest problems first.
All the Glyhps callback are not the issue:
When you draw physically: you would start a drawing by first taking some paper, picking up a pencil, put the pencil down and draw, finish the drawing by framing it and hanging it on the wall!
Translating your code: you are drawing on the same paper over and over again, and only saving the image after you hang it to the wall... 
I will let you try some more
good luck!!
could you provide a simpler example... by eliminating all imports and functionality which is not default (like from GylphsApp)
And every drawing should be wrapped in newDrawing() and endDrawing. You are doing this now at the top of the script (once).
you need color profile data:
like this one https://github.com/haasn/cms/blob/master/Adobe ICC Profiles (end-user)/RGB/AppleRGB.icc
import AppKit
fill(1, 0, 0)
rect(20, 20, width()-40, height()-40)
data = AppKit.NSData.dataWithContentsOfFile_('path/to/AppleRGB.icc')
saveImage("test.tiff", imageColorSyncProfileData=data)
good luck!!
euh, nope, you will need to provide more info
do you have a sample script?
and how is the output different?
thanks
could elaborate why a viewBox is necessary? and how it relates to width, height DrawBot is using.
(maybe this discussion must move to an github issue)