Here’s a very simple setup that works for me. You do have to bind to that OnReachedJumpApex event that you mentioned already. (I usually choose to bind events like this at BeginPlay, for many reasons.)
The Notify Apex bool is not something you’d want to read from — it’s there for you to set to true, and that’s it. Because it gets reset back to false every time the OnReachedJumpApex event fires, it’s up to you to decide which jumps (or other situations where the character becomes airborne) actually set Notify Apex to true, and consequently cause that event to fire.
I’ll try to explain another way if I’m still not making sense!