portable generator to load center
depends, if the 50A twistlock on the generator is fused then yes you can, Otherwise i would tend to think you need to switch out the 60A two pole for a 50A. I'm sure someone who actually took the time to get out their codebook will chime in and correct me if i'm wrong. The grounding and neutral hookups you suggest should be fine. You'll also need to shuffle the breakers around so you can get some sort of interlock kit onto it or a transfer switch of some sort to make two way energization(it'll be in the dictionary next year i promise) impossible.
Sarcasm is my friend
I'm here to learn too, i do mostly commercial/industrial/new construction and this place is a great way to pick up tips on residential from some good electrical minds. Excuse the spelling, my phone has a mind of it's own.