I agree that the quality of the record -- AND its playback equipment -- among other physical factors will dramatically effect the numbers. My "10-14" quote only applies for ideal conditions: a newly-minted, unplayed disc on a high-quality preamp which together with the turntable and clean needles can produce a very low noise floor. Obviously I'm never going to get this with my dad's old Dead vinyl that he played to death, or with cheap needles, or with those crappy Crowley turntables at target....
Anecdotally, on my home system with clean records, I can make nearly-CD-quality recordings, with the differences only really apparent on flat studio monitors or a good Hi-Fi.
Surprisingly, yes. With noise shaping (https://en.wikipedia.org/wiki/Noise_shaping), very coarsely-quantized digital audio can produce high signal to noise ratios in the audible frequencies, via quantization techniques that push the error towards ultrasonic frequencies.
This doesn't violate information-theoretic limits because noise shaping requires very high sampling rates. The 1-bit Sony DSD format (https://en.wikipedia.org/wiki/Direct_Stream_Digital) used a 2.8MHz sample rate.
In the case of vinyl, the effective sample rate is physically limited by the (linear) record speed divided by the vinyl grain size, and to a rough approximation the bit depth would be log of the maximum groove amplitude divided by the grain size. However, the analog cutting mechanism would greatly limit the opportunity for dithering and noise shaping -- for example a needle cannot cut a wave shorter than the tip size.