@BB69,
In 1988/89 I spent some time area cleaning parts of SW Scotland and NE England of the wreckage of PA103, which was spread over hundreds of miles.
The crater at Sherwood Crescent in Lockerbie was caused by the explosion of the fuel in the relatively intact wings and not by the kinetic impact. The second thing to realise is that shrapnel from an exploded projectile is very hot.
So to your summary points I would say that, by comparison with PA103, the wreckage came down in a very tight pattern. The lack of a substantial crater means that most of the fuel was burnt before impact. In my mind this is corroborated by the heavy sooting on the fan blades, which I do not recollect on the PA103 engines that broke off the wing before impact.
So in my view:
Hot shrapnel penetrated the port wing fuel tanks igniting the fuel and starting at least one engine fire.
The plane lost forward movement very quickly, but broke up at a lower altitude than PA103 (which was around 19,000 ft for the major break up IIRC - but, admittedly, the stormy weather on 21 Dec 1988 will have been a factor in the wider spread of PA103 wreckage)
EG