The non-porous surfaces (i.e., stainless steel) can be cleaned and sanitized.
Replace the non-porous surfaces (e.g., o-rings and short plastic gas-in tube, if applicable).
If you haven't bought a dip tube brush yet, you should.
You can't clean the inside of the tube w/o mechanically scrubbing it.
If you don't have a dip tube brush on hand, try using sturdy fishing line.
Pass the line through the dip tube and make a loop.
Put some old nylon hose or a small piece of a rag through a loop in the fishing line and pull it through a few times.
Bleach + water is OK for 10-20 minutes in a SS carboy.
I don't do the bleach treatment every time. Just when I get a new (reconditioned) keg.
I would NOT leave bleach/water in overnight like you're doing with the PBW. Just 10-20 minutes.
I usually seal up the keg and flip it upside down so the entire upper 1/2 also gets a good soak (tubes, poppets, lid, etc.) for 10-20 minutes, as well. This is followed by a good thorough rinse immediately afterwards and then the sanitization step (usu. starsan).