Most IDEs are compatible with ArcGIS, so the question boils down to asking what the best IDE is in general, for which you will get a wide range of responses. Since line numbers and debugging tools are common in IDEs, I don't see any requirements you have that would indicate one IDE is better than others.
Regarding
We thought that PyScripter would be a good option, but it appears that it is a malicious program.
I am not a huge PyScripter fan, but to say an actively maintained open source IDE is "a malicious program" is a bold statement. What information/criteria are you using to come to your determination?