1. Verified, looks ok, the ISBoxer Addon is generating without overlaps (you can see what it is doing by checking out the files in %WoW%\Interface\Addons\ISBoxer).
2. The Assist macro is in the ISBoxer Addon. You can't see if via the WoW GUI AFAIK.
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5. And this is not correct. The Debug Console, if you followed the link I provided, will show you what keystrokes are going to each of the slave windows. From what you described, it sounds like you are looking at the Inner Space console, and not the ISBoxer Debug Console. Basically, you need to know that on your main PC, from slot 1, if you hit Alt+A, that your slaves receive the 162+BACKSPACE keystroke from is1. If they do not, then that is where the issue lies. If they do, then the problem is either that the ISBoxer Addon is not loaded, SHIFT+BACKSPACE is bound to something else, you are getting some
Assist Delay, you have a different Addon interfering. A very simple test to cover most of this, is on your Slave PC, pick a toon and hit LEFTSHIFT+BACKSPACE. They should assist the slot 1 toon for your Main Char set.