Thanks for the appreciation.
Regarding your query, you can use setExact(time) while creating the JobRequest through its builder to make your job an Exact Job. Where time can be the difference between your target time and current time in milliseconds.
But remember that exact jobs can not be periodic so once you apply setExact(time), you can not use setPeriodic(interval). So what you can do for your requirement is just schedule another exact job for next Monday 8.30 am inside onRunJob of your Job class. This way you can trick this to act like a periodic job running at an exact time every Monday.