Yes.
Not really, take Toughness as a feat.
Yeah, not even remotely a choice. Extra talents are usually better. By the time you're level 12 an extra 12 hp on top of 54 - 78 hp (avg hp with +0 con mod to +2 con mod)....the 12 isn't terribly significant. At best it might give you one more round to act before going unconscious or dying. But probably not even that. By level 12 the amount of damage you're going to take in a round is going to be large enough that those 12 hp just probably aren't going to make much of a difference, but that extra talent could certainly mean doing something more in combat to save your bacon.
One rogue talent is worth a feat, and many rogue talents are better than feats.
Increasing HP is the equivalent of taking the Toughness feat, which adds 1 HP per level, like all your favored class bonuses combined.
And if two rogue talents are worth two feats, and 12 HP is worth two-thirds of one feat...
basically my maths Saethori