1.It ain't specifically mentioned but i can tell you in the nutshell that only Bhopal Shatabdi and Chennai Rajdhani have LHB coaches as far as trains from Agra cantt are concerned.
While on Agra Fort only Jaipur Agra shatabdi has LHB.
Basically LHB is given to most of the Rajdhanis/Shatabdis and some express trains (for whom its mentioned somewhere in the train page)
2....
more... Not that I'm aware of.
3. The PNR forum is not VERY extensive as far as your research is concerned. Only a few PNRs are posted and the number of entries IN NO WAY give any data about total number of tickets booked.