Foreword: I am a player of AD&D 2ed and am very fond of the material published for this system.
I would keep the setting as it was before the publication of the Campaign Setting for the 3ed (still a truly extraordinary manual!!).
I would use 1369 AD as the starting year, immediately after Time of Troubles.
Of the 3ed material, which I think is excellent, I would keep the details of the races, languages, prestige classes (turned into kits) etc. while I would completely ignore anything published after 3ed.
On the level of events, I would always stop at 1369 or 1370 AD, avoiding the introduction of events such as the reappearance of the city of Shade and others.
Yeah, the Shades are something I could do without. During the 4e era, I played in some excellent Living Forgotten Realms adventures that used Returned Netheril as the bad guys, so I won't say I didn't care for the metaplot development, but if there's one thing I can attest to, is that Toril has no shortage of BBEG's to choose from, so adding more seems kind of messed up. I mean think about it, you got:
*Megalomaniacal spellcasters.
*Thay (or is that the same thing?)
*The Zhentarim (these guys refuse to die!)
*Gods.
*The Cult of the Dragon.
*Drow.
*Interlopers from other planes/outer space (I see you, Acererak!)
*Monsters (like, normal monsters, Trolls, Or...Owlbears, that sort of thing)
*Dragons
*Ancient Evils (Phaerimm)
*Demons and Devils (let's put the Fey'ri and the Tanarukk here)
*Corrupt Nobles (is there any other kind?)
*Jumped-up Thieves' Guilds (Fire Knives, for example)
And most of this was before we also had the Horde, Returned Netheril, the Abolethic Sovereignty, the Cult of Moander, and anything else I'm forgetting at the moment.