Mix three parts water with one part alcohol and a tablespoon or two of dish soap in a spray bottle. Spray generously after the worst of the sun has passed to prevent leaf scorch. It should take care of the aphids at least.

Natural pyrethrum is approved for organic culture of vegs and greens, but you’d of course have to find it and use the correct dosage. Organic greens are bunny safe. Try to use insecticides that are not systemic-acting. Systemic acting compounds can’t be rinsed off.
Q8’s tip will get rid of the aphids though. As for caterpillars you often have to remove them manually.
Growing marigolds next to veg won’t spoil the veg. It’s debated if marigolds (calendula) are edible for buns or not, mine won’t eat them. But the plant isn’t crazy toxic, so they won’t contaminate the rest of your crop.
The type of plantain I feed my buns is plantago major. Sometimes plantage lanceolata (ribworth) is sold dried as a bunny snack, but my buns won’t eat it and I’m not sure it’s that great for bunnies, cattle can get tummy trouble if they graze on pastures with a high percentage of ribeorth. I’d go for the plantago major. It’s supposedly very healthy for humans as well as buns, but I can never pick so much that there’s any left for the humans.

Cabbage worms i.e. the caterpillars you’re seeing and cabbage moth larvae can make considerable damage to all cabbage (brassica) plants. They seem to be common all over the USA nowadays. The best thing for a small garden is to hand-pick them and drench them in a bucket of soapy water. The cabbage caterpillars come from the eggs of white butterflies with black spots on their wings, cabbage moths look like regular small moths.
I have built a tent of mosquito netting for my cabbage plants, but you of course need to do that early in the season. What you can do now is probably just pick the caterpillars and larvae. Look on the underside of young leaves for the larvae. They will consume all the soft parts of the leaves if you let them be.