Practise, practise, practise.....
I'd start with ISO 800 and at least 2-3 min subs - the maximum will be determined by your sky glow/ background.
Sounds like you may have the wrong camera for guiding....
Think about something like the QHY5 or ASI120 - easy to use and all software talks nicely to them.
Onwards and Upwards
[EDIT]
It appears that the ProStar is a pretty capable camera....
https://www.myastroshop.com.au/guides/ps-lp-guider.asp