I think that is overly complicated for your problem.
Determine if Inspection is valid
If you have an Inspection Plan, that is likely already entered and exists in the app.
As the Inspections entries are made, all you need to do is insert an expression like the below in the Valid columns App Formula. If I am missing any processing steps that makes it less simple than this then please let us know.
AND([CheckPoint] = [_THISROW].[CheckPoint],
[Start] <= [_THIDSROW].[Time],
[End] >= [_THISROW].[Time]
) > 0,
Basically, if there are any rows where the CheckPoint matches and the Time is between the Start and End times then Valid = true. Otherwise, valid is false.
Sending a Notification
When an Inspections row is either Added or Changed (depending on your apps entry process), you would have a Workflow triggered that sends either an email, an SMS(text) message or a Push Notification to the target recipient.
I’ll assume you know how to create such a Workflow. If not re-post here.