I expect as usual more intelligence exists, such as the specifics of the shootdown. There's some reticence to come out and say who it was in plain language.
As to how the airframe broke up, I suspect that was inevitable once a large explosion compromised the integrity of the fuselage; a 70lb warhead is so big and a non-evading frontal-quarter 777 such a textbook target that it would have been almost test conditions.
It looks like the wingbox and remnants of the wing and centre fuselage fell in one piece with the engines (unusually for a break-up) attached, where the big fire is in all the photos.
I hope the CVR and DFDR haven't been irreparably damaged by fire as it looked like they didn't have much to control the fire with. Not that they will be that useful.
I still wonder what the hell the shooter was thinking, and it's extremely fortunate they didn't knock down the SQ flight, too, seeing as it must have appeared as a similar return within a couple of minutes of MH17.