@AngeleToR Thanks for the update and glad you got it going, well done.
However I would not recommend your advise on using the nut user as it is still potentially a security risk. The NUT system makes no assumption that this nut user requested during config is a system user and there is better separation if it is not a system user. Did you find that you were unable to use the monuser suggestion or any other non system user as it really is a good idea to not use a system user as it’s credentials are in no way considered as ‘precious’ as normal system users? Also using a system user very much blurs the distinction when in fact it is used completely independently, hence the suggested ‘monuser’ example for those that are not aware of this. And the password you enter there is one you are creating for that user at that time.
This is where I agree with you that the tool tip popup and docs could be better, however. I have on your suggestion opened an issue to address this in the doc repo.
Just my opinion and also removes the requirement to command line it; there is as well additional value in having this user be explicit, in my opinion, given the network nature of NUT.
As per your Shutdown after time period request I completely agree and hopefully it’s just a matter of time before that gets implemented via the Rockstor Web-UI. In fact we have an issue open on this very thing:
Bit more tricky to do percentage of battery as not all UPS’s can reliable indicate / report this unfortunately. But the after a set time thing is a build in for NUT due to the popularity of the request for the same.
This issue in turn links to an existing forum post on the same feature request. I have also added a link to your last post in this thread to that issue so that this thread also might be informed of progress on that issue.
Glad your happy for the time being and chuffed that it’s working for you (though I’d follow the suggestions re user myself 
) Also I believe the auto port doesn’t work for serial ports but thankfully USB is becoming more popular even in the slow moving UPS hardware field.