For the distance to the car in front - you really only need a few good feet, (10), enough for you to easily vacate if required.
However I would have :
(traffic slowing with you)
controlled the traffic earlier to enable a good, gentle, and gradual, slow down of rear traffic long before I (and them slowed to a stop) stop,
(no visible traffic behind)
I would have, allowed a much longer slow up space or gap (5-10sec gap), and controlled from there - slowing as I approach the rear car, always allowing for the rear traffic to react to my control actions, Major vigilance.
(rear traffic becomes visible)
with gentle braking, and a slow creep up to the last queuing car, to allow that the rear traffic is not paying attention, and needs to be slowed (brought into check), under your control.
Then I would still be constantly vigilant, checking all about me using my mirrors and views for any likely impact from all directions. I would not leave my foot on the brake, as if you were to get hit - your whip lash injury is worse and so is your car damage, but if you leave your wheels turning towards your planned escape route, and release your brake, then if you get hit, you're off and out of harms way, with as little damage as possible. However far better that you have already driven off, in your preplanned direction! Pre-planning here is absolute key.
Well I am saddened by the thought that the driver skills may really start to be lost in my short life time. With modern technology are we really going to improve safety and ability by removing skills from the driver.
Is this to pacify the A to B drivers who want a gizmo car? How very sad.
I find that garages screw up my handbrake by yanking it on far too hard, it should be 7 clicks. Once learned you can then press the button, and check for stretch by counting clicks occasionally. I have found that the polyurethene, (plastic) can be damaged or it cracks, and so after a time I need to replace the handbrake for this reason, so I have spares - they are very simple to fit - takes about 30 minutes and that includes getting the tools ..
I cannot see how pressing the brake pedal in my car, makes any difference to the handbrake efficiency. The handbrake shoes are separate so I have not done that. I assume that your car has a different set up which interesting.
I worry about having ABS, never mind something that turns on your handbrake - imagine if that happened in mid overtake or mid corner - yeesh - very worrying. I like to be in total control, and would never rely on a chip! And I absolutely know that Paul would be whole-heartedly agreeing with me.
I suppose a swift snip to a few wires should sort out most of the non-sense (for me you understand). And as for the seat belt well you don't have to be 'in' the seatbelt, after all the States were clicking in the seat belt and then sat down and drove - that was in 1979 ! So that one is easily solved for the like s of garages etc. (Unless it is a weighted seat) ....