The specs for proper timing are:
The top of the plunger lever above the frame .060-.065 inch with all trigger pretravel removed and .090-.095 inch with the trigger held full rearward.
99% of the time, the #2 lever will correct a slow timing issue in a stock pistol. If Colt won't send one, try Cylinder & Slide. They're pretty cheap, so ordering both a #2 and a #3 might be the best approach.
NO gunsmith worth his or her salt will de-activate a factory installed safety device.
Not if he's smart, he won't. My older pair of 1991A1 range beaters have been both so modified by yours truly. I'm the only one who fires or even handles the guns if they're loaded. No exceptions. If your best buddy shoots himself in the foot...even if the inclusion of the parts would have made no difference...you're open to a ruinous lawsuit even if you win...which you probably won't.
And don't think that your best-bud-for-life wouldn't sue you. After a year out of work, when his medical insurance stops paying, and one of his cars has been repossessed, and the mortgage company is threatening to forclose and his kids' college fund is rapidly depleting...your assets will be mighty tempting.