1) Am I arrogant for discrediting the everyday-ability of modern carbon? (There are so many offerings)
Not really. But you won't be happy if you don't get either a genuine Litespeed or at least a titanium frame, because that's your mindset right now.
2) I don't have a real parts bin, is piecing together a build not the most patience-molesting task... Should I just bite the bullet?
You're relatively new to the road bike world and don't have a parts collection. Just buy a complete bike and be done with it.
3) Am I sentimental/fixated on going for another Litespeed (I really do believe in their quality and value, relatively speaking)? What other bikes would you recommend?
Forget Litespeed; the name was sold so they're no longer what you remember. You want titanium; get a
Lynskey. You could easily race their Sport Riding, Gravel, or Cyclocross models. Don't get wrapped up in bike label names i.e., Sport Riding, Gravel, or Cyclocross. Specs between bike styles have become so fuzzy as to be almost meaningless.
4) Where else would you look for a groupset / part bundle?
I'm not in tune with all the on-line offerings. Others here can offer better advice. I did have good luck with
Excel Sports, however.
You CAN get a jack-of-all-trades road bike, with the only trick is to swap wheels from your commuter wheels to "fast ride/racing wheels".