1) For NTSC B&W it should read back 0x00 or 0x02, NTSC-M/J or HTSC-433 assuming the input timing is one of the NTSC formats
2) SPD_BURST_LOCKED_RB indicates the device has locked to the color burst, SPD_BURST_LOCK_RAW indicates the same thing but is used as part of the interrupt logic.
3) Assuming you have autodetection for SDP turned on as outlined in the Hardware manual section 7.3.1. SDP_STD will indicate which timing format you have. And you can use SDP_BURST_LOCKED_RAW to determine if the incoming signal has color on it.
Just a note, if you look back in history, timing and levels were used to define various black and white video formats. Color information was later layered on top of the timing and levels where the color burst phase locked the color generator so the color information layered on top of the levels could be decoded.