While I do appreciate your situation and understand your frustration, I must first address your most serious accusation that this extension is malicious in some way. Your main cause for thinking so is the fact that one of your extensions was disabled. However it is not uncommon for Firefox extensions to conflict with each other. I do appreciate you reporting this fact. But it is misleading to label this as malware.
In regards to the unfortunate difficulties you have been having, it is important to note that this extension was designed to work on much older systems and does work very well with those systems. In addition, this extension was not designed to print pages into one pdf the way print to PDF is.
That being said, I am not against redesigning this extension to make it useful to users such as yourself who are working on newer systems and require more settings and abilities.
As it stands, I am a bit constrained in the amount of time that I can spend on hobby projects such as this extension. However, It has been a long time since this extension has been updated. So I may take a look at it again to see what I can improve. My priority of course will be inspecting and resolving a possible conflict with NoScript.
In order not to mislead other people who could find use in this extension, I would greatly appreciate if you would modify your response to remove the word Malware, unless you can of course present the results of an actual security scan that identifies this extension as harmful to the safety of your personal information or overall safety of your computer.
If you feel a need to warn people of your experience, perhaps you can use the word Incompatible, or Conflicting instead.
Thank you for your input and understanding,
Universal Print Developer