Last performance was probably 2nd October 1992; I have a bootleg from this date with ToL on it. I have a few other bootlegs after this date too and they all have TR so unless it was performed in Madrid, 6th October then Barcelona, 2nd October was the final performance.
I doubt his Father's death had any influence. I don't know him (obviously) but he doesn't appear the sentimental type to me. It is more likely to be that he doesn't feel he could do the song justice any more, certainly in terms of the energy the singing requires. Even on the OES tour it sounded quite lifeless. Also, the 96ers are more Nashville than Rock 'n' Roll, the very reason he has never performed the song in his solo career. As Ed rightly said - The Dullards. Worthy musicians, but dull for the music of DS.
I think you are both right: initially it must have been the sentimental reason. In 1996 Mark was still very energetic and could have performed TOL with no problems. Now he would probably struggle, so even though 23 years of mourning is enough, he would not play it.
This being said, am I the only one to think that DS songs were very well played in 2015 ?
-Sultans: renewed energy and old licks.
-R&J: sax is back and with a new middle solo
-Brothers:love this version, intro is back, synth is back, and yet not as slow as 96 or 01 (I like it fast)
-OES: love it, I prefer sax over pedal steel
-YLT: superb intro (She's gone), more authentic feel that in 92 where it was kind of robotic
Only TR I think lacks energy, I prefer 2010 or 2013, and actually 96/2001/2005 without the infamous karaoke mode. Although i still love to hear TR, whatever the version.
I find myself listening to the 2015 versions more than any others. Also I love the arrangements of solo songs like Speedway, HFB, KOG (listen to the Manchester versions where the synth can be well heard, very nice !).
Not that bad for so-called "decadent times". My 2 cents.