The bottom picture looks like a slug and they love cabbage.
I would never grow cabbage NOT under a row cover and I usually have to use some organic slug bait around the plants right after planting.
DSC00392 by
Brownrexx, on Flickr
Here is this year's crop. I didn't want to make sauerkraut this year so I cut back to 4 plants but I grow cabbage every year and never have insect problems.
20190607_182747 by
Brownrexx, on Flickr