I can only assume you've already made sure whatever is outputting the sound (TV/speakers) is working properly, and the in-game volume settings are correct, so... if re-downloading the game had no effect, it's likely a bug with your console itself. In this case, the only solution I can think of would be to reset your PS3's memory (I.E reinstalling the console OS) in order to revert it to "factory default" settings.
As for the buttons, it might be your controller. For both issues, try playing something else on your PS3 and see if the audio and aforementioned buttons are working correctly. Either way, I can't think of anything else that can solve your problem. I've never heard of the game itself having any such issues, so the only conclusion I can draw is that it's your console itself...
Yeah, other games were working fine. I just restored it to default settings and that seemed to fix it for a few minutes, but then I was playing--and while the sound never went away like it did before--it stopped registering B and D inputs once again. It's really weird, because macros (like A + B on R2) also would ignore the kick inputs, for instance, but once I paused the game it would have no problem registering X and O for the menus and stuff, and if I re-mapped punches to X and O, it would register those inputs just fine. So it was just the kicks it would refuse to acknowledge.
But yeah, Chronophantasma, Darkstalkers Resurrection and 3rd Strike all seem to have no problems either with audio or with registering the button presses. This is so frustrating. I was just getting back into the game too.