Two parter here
Q297a: Would a Wizard 1/Dread Necromancer 7 (in any order for class levels) have two familiars or just one? I ask because they have two lists of choices with no overlap as well as the fact Dread Necro's don't get their familiars at level 1.
Q297b: If the answer to part a is "yes", would Stitched Flesh Familiar apply to both familiars?
A297a: These class features have identical names, but have different effects; I believe you need to have both identical names and identical effects in order for the ability to be considered "the same" and thus overlap. So yes, you would have two familiars.
A297b: If this is correct, I honestly have no idea. The feat specifies "standard familiars available in the
Player's Handbook" and refers to the special ability granted the master by a familiar of a particular kind, so the intent suggests that it would apply only to a normal familiar, since it is clearly not adapted to Improved Familiar (which is the list, with some modifications) that a Dread Necro chooses from. Were a Dread Necromancer to grant you a normal familiar, however, I believe you could select a stitched flesh familiar.
Q298: You cannot deliver a touch spell through an unarmed strike at the end of a charge, right?