So does anybody have an answer. From my perspective anything less than a total social collapse is just a temporary emergency situation as all social rules and institutions still exist and function.

My first wiseass thought was, "Go ask the Amish" but I didn't want it to sound rude. It depends on your perspective on life and how dependent you are on modern conveniences. If you're bedridden and on a respirator and/or dialysis machine, any interruption of electricity is SHTF. If you're a city dweller in a densely-populated urban zone, it could be a loss of electricity in the summer with a suspension of city services and/or a major watermain break. If you're Amish... I think angels and trumpets need to be involved or something....

I agree with your summary but it's a matter of needs and degrees. What defines SHTF to me is desperation - the longer a person feels desperate, the less those rules and institutions will guide their behavior. The more people or entire communities share that growing desperation, the closer to your referenced collapse you get. If my house gets hit with a tornado, it would royally suck. But if ours is the only one, our neighbors would absolutely take us in, we have homeowners insurance, my wife stays home with our daughter anyway and I can carpool, public transport or bike to my job ~ 12 miles away. Sucks, don't want it to happen, but not a desperate situation. No SHTF for me.

IMO SHTF is anything that takes you out of the bump and grind of your regular everyday life.  Whether it's mother nature, or some human caused event (riots, war, etc).  In my mind, if it's a long term event that has thrown you/the people around you off track, it's  big SHTF.  to me it could be anything from the meltdown of western civilization to a storm knocking power out.

It all depends on whether or not I have beer stored up.  Things are always better if you can sit down and have a beer and ponder.  

I have been without power for a week or so in both summer and winter.  No problem except ya got to get up a little earlier to get things going.  

If I was laid off work (which aint happening) then that would be a big chunk of spam hitting the fan.  Injury would  be the same.  The definition is different for different people in different areas.

SHTF to me is a little higher grade of "bad" than a simple ice storm etc...SHTF has to have immediate, life altering consequences.....Just being without heat or electricity in a local area doesn't qualify. If a "Three Day Kit" will get you by....it ain't SHTF! It's a minor inconvenience.

Now, it could be a tornado just hit your house. That's a very serious situation-going to take more than a 3 day kit to recover-that's SHTF. I think an armed gang advancing on your property constitutes SHTF.....as it involves the possibility of immediate death or maiming. Things that could be permanently life altering qualify as SHTF.

The next level is TEOTWAWKI, meaning, the world has gone batshit crazy, no expected police response, critical infrastructure has collapsed- water, electricity, food delivery etc.....This is Madd Maxx kind of stuff.

Anything that makes YOU go ahhh shit what now??  It will vary from person to person.  Example blizzard no power etc my neighbors freak out what are we going to do???? I play board games or read after putting freezer/fridge stuff in a cooler and cook dinner on a propane stove---for them big deal for me a couple free days off of work(we get snow days where I work so if the road is closed time off without using vac/sick leave).  There are different severities but that is my basic philosophy. YMMV