Mr Bamber,
Your first post said:
If (and I am postulating from the picture alone so I caveat this statement heavily) the left engine pod had been in contact with the ground on the roll out it would produce a left yaw
This is wrong. The friction force acting on the engine will be much LESS than that exerted on tyres. So, there will be a danger of the a/c slewing to the RIGHT if the pilot stamps on the brakes too hard. Well done flight crew for keeping it straight, on the runway, and stopping in time. That will have required a cool head and a light foot.
Btw I'm not a pilot.
Both of these theories could be correct depending on the degree of braking used. What the original poster (who I assume is a pilot) meant was that dropping an engine onto the tarmac will generally give you a level of retardation on that side which will be greater than you would expect on a normal landing at touchdown (bearing in mind you often don't even necessarily use brakes straight away especially on long runways). You are also probably correct that using heavy braking you could get the other (good) gear to provide even more retardation if you hammered it (you would be amazed at how powerful the brakes of an airliner are when they are really needed). You then have the added complication in this case that the partially collapsed gear has only been pushed up until the engine contacted the ground and remained in contact with the runway according to the photographs, and for all we know may have continued to provide some braking and directional control. BTW the nosegear has no brakes, although it does have steering which may also have been used by the pilot to stay on the runway of course.
Your second post could be way off with the numbers - speed more like 130 kts maybe at touchdown or less with double engine failure if they tried to "stretch the glide" as it is known depending on what position the flaps ended up in for landing after the reconsidered go-around. This gives only just over 40% of the kinetic energy your 200 kts assumption gives. On the other hand maybe they were at 200 kts needing to get the thing on the ground before the concrete ran out, which they appear to have done successfully.
The other forces that you are neglecting to consider are those provided by the rudder and nosewheel steering. Pilots instinctively use the rudder to keep straight on take off and landing and it is extremely powerful until the speed reduces when the nosewheel steering can then be used. It is easily possible to land and just use the brakes on one side for example, using the rudder to keep straight (this has to be the case of course in case the brakes fail on one side).
Ex-737 driver with a physics degree and 20 years on commercial jets BTW.