Looks like you are on the right track. Collimation looks pretty good, but the defocused star is a little big to be really sure of collimation. Something about half that size will be more accurate.
Field curvature is normal for RC telescopes and like you said it will be less evident with the smaller sensor. I can be sorted with flatteners and reducers too.
The eta image looks sharp the detail looks as it should. You can compare your images to
my eta image with the RC8 and a 40D if you like.
I look forward to more images coming from you.