I've never seen WMC not get accurate TV channels if the setup is done correctly. I have, however, seen it not have the most recent channels propogate, such as in New York, NBC 4.2 was NBC NY Nonstop and became COZI TV a week ago, but still the guide says it's NBC NY Nonstop.
You can always edit a channel and re-source it in WMC.
Depends on the software you're using for codecs.
I use Shark007's Win7 32bit and 64bit coded packs and have tuned them quite a bit.
The main thing for you to try would be the Win8 packs (32bit, 64 if you're > 4GB RAM).
On BOTH, you'd need to check use the recommended options, then on the SWAP tab, disable Windows Audio. This would force LAV Audio splitter to handle your WMC live TV audio.
You'd need to post how you connect audio up (e.g., AVR, powered speakers, TV's audio, etc) on on what connection (Analog, Optical S/PDIF, etc).