Use excel to calcluate average and stdev of time differences in a time series?

Question

EDIT1: download file with 2 days of real data

My home automation controller collects data from several 4-in-1 motion sensors in different rooms of my house. The sensor prioritizes motion, sending motion reports every few seconds, but also independently reports temperature, humidity, and illuminance. I am trying to determine if the temp and humidity reports are sent frequently enough to automate control of heaters and exhaust fans.

Sensors independently report each category to the controller, which sends data to excel. Sample data below, but without motion reports that clutter up the real data.

A pivot table generated from the raw data:

Answering the question of frequency takes me several manual steps. Sorting/filtering the dataset for temp/humidity by room, then manually adding a time diff column

where time diff = (<current Date-Time cell> - <prev Date-Time cell>)*24*60. I then calculate the average and stdev of minutes between reports by manually selecting, in turn, each room/category subset in the time diff column; once for the average and once for the stdev.

After a few more manual steps, I end up with this desired result:

BUT I have to do it all over every time new data is added to the table. I'm certain excel can do this automatically, but I didn't find a solution through pivots, power pivots, slicing, or queries. I'm hoping one of you excel gurus can help. Thanks!