Well, on range I've got some potted refs that state the 200 had 4850 miles and the 500 had 4580. Looks like a typo, but I recall Flight quoting similar figures (about 300 miles extra for the 200) in its proper old commercial aircraft surveys before it became an accountant's mag. All very odd if true since the 500 was supposed to be the long-ranger. Yes, the 250 was an aftrmarket mod by Delta.
Interesting to hear DLC is still operational. Had heard it had been stripped off years ago by some ops and had been disabled by others, leaving precious few if any operational by now. Must cause extra drag and noise on approach, surely..?
And yes, the active ailerons were put in so the wing could be stretched by 9ft without any structural beef up. Which still leaves me wondering why no active ailerons on other types. (I may be wrong here, since 320s, 330s, 340s, 777s and all that leave me pretty cold.) If the reason was a patent issue, Lockheeds surely could have sold their rights as they were desperate for TriStar funding. So the insiduous thought inside me mind is - they were not as good as winglets, etc.
On reliability, I'm sure it's improved, but can't help recalling what I heard from Court Line people donkeys years ago. Suffice it to say, thank Goodness for the Laker Tens that regularly had to come along and lend a hand...