Alright, I figured a solution out. I created a Flag_Staus_Days Field If(Status="Active";Days) I can use this result for my Average fields..
Seems like you should use:
"If(Status="Active" and Not IsEmpty(Date_Start) ; Get(CurrentDate)) - Date_Start + 1)
Note that = 0 has been removed.
Don't see any way for status = "inactive" to produce a result with the above calculation once you modify it as shown.