For the neck, i suggest extending it up a bit further behind head. i normally put a semi circle on the end of the neck so if something is revealed it's more of a curve.
Next, check the head position strength (i think in face behavior). Set it to zero. I think it's not zero, so head is drifting away from body a bit. This works if head is a lot bigger than neck, otherwise set it small or zero.
For the eyes, what matters most is the Left Pupil Range and Right Pupil Range tags. They set the range the pupil can move. I would go through all your layers around the eyes and check where set. Normally eyeball gets tagged. It could be not set, or set more than once. Both are bad. The whites of your eyes should probably have it set.
oksamurai has a good video on eyes on his channel - but i keep forgetting to bookmark the link. This is my blog post on eyes: https://extra-ordinary.tv/2018/04/21/debugging-character-animator-eyess/