160nc:100, pull 1/3 stop (I like the lower contrast a tad)
400nc:250, run normal
there is no definitive answer to your questions unless you test. This obviously would involve the meter you intend to use, internal or handheld.
Include a colorchecker chart or gray card(at least) in some of your shots.
Are you wet printing, or doing the hybrid process? (I do both, and I've found the hybrid process allows for greater contrast control). My speeds work for both for me.
Shoot one roll @ 160, one at 125, and one at 100, and 80(if you want to be very thorough) .
Develop 1st(160) roll @ NORMAL(according to 3:15 or normal at the lab), scan or print. See results. See if you like what you see.
Develop subsequent rolls(2-3 or 2-4) at normal,etc...
You can see where I'm going. I have homework to do
best of luck!