Totally agree 100%. I posted something about this a couple of months back. The preoccupation of The First with Vampires-with-a-soul seems to be pretty consistent. Possibly with Angel, The First unknowingly had the wrong Vamp, or possibly it doesn't matter which, as long as the soul criteria is there.
As for Buffy being ressurected, I got the feeling that it was the first time that caused the disturbance, not the second. My conjecture was also that there was possibly an issue with the central power driving the slayer line. I don't believe that it just multiplies in and of itself, as I didn't believe the source was infinite. That conjecture has gained alot more credence after the episode where Buffy goes through the portal, in my opinion. It's still nothing but a theory, but hey, aren't theories fun?!? 🙂
Knowing what we do now (and having never read a spoiler - it takes the fun out of theorizing) I would guess that there's still an issue with that power. Clearly Faith is no weaker than Buffy, at least not physically, so that isn't an issue. That leaves me wondering how 2 slayers have inherited equal power from what is now definately known to be a finite power source. One possibility is that some of the power is noramlly detailed towards manipulating events or cosmic balances to keep The First out of the picture. I'm sure there's lots of other possibilities tho. Maybe Buffy has ended up borrowing her (reborn) share of the power from the NEXT slayer line (kind of a time-transcending event). That would certainly explain why the First chooses now to act, and also why Buffy is described as the 'Last Slayer' or 'latest in the line' (Not sure about this one, but I heard someone mention something about this earlier in the forums). Anyway, just theories. Dust in the wind 😉