1. Which is "closest" is a tough question. The repro of the New Model Russian is in the right caliber (.44 Russian) and close in dimensions but mechanically different and I feel it is "beefier" that an original. The repro Schofields are in .45 Colt (and maybe others) that the original Schofield never chambered, and consequently the cylinder and (a few other internal things) are different. You can shoot .45 Schofield in it, but that makes you more authentic, not the piece. I believe even the S&W-made Schofield repro is different from the original--it's in the right caliber, but as I recall the firing pin system is different. Maybe the forthcoming American? Although the pictures look like a 1st Model American, but I understand it is chambered in calibers other than the original .44 American. With a slight frame adjustment they could've maybe reproduced the Old Old Model Russian (I get the desire to chamber it in a readily available caliber, and .44 American is not that), but it doesn't look like that's the plan. Plus can't tell dimensions from the photos. So, I guess my answer is, I dunno.
2. Among S&W Single Action Number 3s, the American Model, Old Old Model Russian (both on the American frame), the Old Model Russian, and the New Model Russian had the topstrap screw. All are "normal looking" screws except the New Model Russian, which has a screw head approaching the diameter of a dime. The New Model and the Schofields don't have the top screw.
3. It has been possible for me, at least, to unlatch a Schofield by pushing into the holster too far. This was with a military flap-style holster. I solve the problem by cutting away some leather where the latch could catch. There are holsters where this would not be a problem.