Hi @Slloyd ,
You could use multiple Flows to correspond to these scenarios.
3 days, 1 day before the event, the two Flows are similar, the only difference is to change the parameters in the addDays() function to 3 or 1.
Image reference:

For "2 hours before event", I don't have a suitable solution for you currently. If it is accurate to the hour, it seems that it is difficult to achieve through the current function.
Best Regards,