Now your questions make perfect sense to me.
It sounds like a fun project. I look forward to seeing more of it.
I doubt there are any stand-alone IDEs for AngelScript, as the scripting library is for embedding into application rather than something to create standalone programs with. For this reason the IDE would have to understand the application in which the scripts will be executed in order to be useful. Most users tend to write their own IDEs as part of their content creation tools.
If you're only looking for source editor with syntax highlighting though I'd recommend Notepad++, or Scite. You can visualize the AngelScript code as if it is C++ and the syntax highlighter does a pretty good job.
If I get iterative execution (I really have no idea what to call it) working well enough, I'll send you a patch. It shouldn't be too difficult. Even if you don't need to know the opcount of the execution, there are other situations where you want to limit it without having to change the script itself.