Engine Oil Viscosity Question

It is an accepted premise and technically make sense that most of the engine wear occurs at start up. To minimize friction, engine components having metal to metal contact needs to be lubricated immediately the first few seconds after start up. My question is, would it be better using a 0W/30 visconsity oil as opposed to using a 5W or 10W-30 viscosity oils?

My other question is: In a full flow oil filter (as most stock oil filters are) what happens to the oil pressure flowing thru the filter as it comes time to change oil and filter? Does it deteriorate just like air filter? Does this indicate that the amount of oil (in oil filters) and intake air (as in the case of air filter) decreases as theyare being used? I use K&N air filter and I wash it with the "kit" everytime I do oil change. Wouldn't it be more prudent to replace the oil filter twice per oil change? Unless you have a "by-pass" oil filter.