Hey PG: Great observations, research, and analysis. One thing though . . . is Brian playing a Strat or a Tele? It's hard to tell because he's wearing black trousers and the black guitar and pick guard all kind of blend, but I think it's a Tele. It looks like that top curve at the base of the neck comes over and right into the neck without making that deep cut that the Strat makes. Splitting hairs, I know . . . ;) But this may also help determine when/where this performance took place. Also, I believe the Tele has more of that rockabilly sound than does the Strat, and would be the guitar of choice until Brian switches over to the Red Special.
Cheers!
Definitely a telecaster. Besides the fact that Brian never really played a strat (until the 50th Fender Strat Anniversary Party) and the fact that he used a tele on the original recording of CLTCL, you can also see it clearly if you look at the headstock and the body when he moves away from Freddie...
Btw, did anyone notice that John fucks up after the a cappella bit? Around 2:06 he skips a bar and is playing the wrong thing for about 2 bars. He still looks as cool as always though :-)
About Brian's Stratocaster (not Tele)- on early concerts they used this quitar as a back-up. You can see this on some fotos from Rainbow 31.03.'74 (for example).