3 - The ammo is plentiful in my area, and in my experience, it was one of the only reasonably commonplace pistol cartridges that did NOT disappear from store shelves during the recent post-election buying panics.
5 - The sights come in two varieties, neither particularly good IMHO. Military guns and a handful of commercial guns came with a fixed, rounded front blade and drift-adjustable rear notch. These sights are about on par with most vintage (1960s and earlier) military pistol sights - durable and serviceable but smaller than most shooters would prefer. The remaining commercial guns came with a fully screw-adjustable rear sight and a taller, serrated front blade. While they sound good in theory, IMHO these sights suck quite badly for combat/CC use, as they are far too narrow for fast acquisition and the rear unit has a reputation for breaking off quite easily if the gun is dropped.
Just as an aside, the commercial Makarov was actually sold in a double-stack version, usually labeled IJ-70-18AH or -17AH. These accept a 12rd mag or an AWB 10rd mag, and curiously, standard single-stack Mak mags also work. However, I would recommend against one of these pistols, as (a) they have a kludgy and overly thick grip, negating one of the standard Mak's major advantages, its slimness; (b) AFAIK they all came with the aforementioned lousy adjustable sight; and (c) 10/12rd mags are reportedly quite hard to obtain and resultantly expensive because most pistols were sold with a single mag and the importers did not bring over many spares.