I would take the fresh grass out. I would be concerned about the possibility of it getting moldy then the mother or babies eventually eating it, which could prove deadly to them. Save all the fur, remove the fresh grass and replace with hay. Make a hollow in the hay at the back of the nest box, replace the fur and the babies. Then provide plenty of hay outside of the nestbox for mom to eat. She is eating the nestbox hay because she is hungry. If you haven't already and mom is being fed limited pelleted feed amounts, you need to gradually start increasing her pellets over the next week so that she is getting unlimited pellet amounts or close to, but also make sure she is getting unlimited hay and eating a good pile of it in a day as well. Mother rabbits need tons of energy and usually end up needing about 3 times their normal amount of food at least.
If any of the babies are clearly cold to the touch, you need to take active measures to help warm them up. You can hold them against your skin and use your body heat or some sort of warm pack. You need to be careful about not allowing them to overheat though, so carefully monitor them as they warm back up. Once back in the nest, as long as they have plenty of moms fur they can burrow under and all stay close together, that will continue to keep them warm.
The baby that seems to be flailing about, has it had a plump belly from being fed or is it starting to look skinny with wrinkly skin? If it missed being fed, it would be starting to be a bit frantic and feeling starved. If so and especially if it is looking wrinkly and dehydrated and the other babies aren't, you can try holding mom on your lap and while carefully holding mom still, bring baby up underneath to allow it to nurse. It works better if you have someone to help as you have to be careful so mom doesn't injure the baby trying to get away.
You need to make sure mom is feeding them at least once a day. They should have very full bellies at some point in the day if she is. If she doesn't feed them within the first 24-36 hours, you may need to step in to help. If it gets too close to 48 hours without being fed, they will start to get too weak to nurse.
If mom is disturbing the nest too much and you feel she is putting the babies at risk of being injured or stomped on, you can as a last resort, remove the nest box and only return it to her twice a day in the mornings and evenings to let her nurse them. I would only do this though, if I thought the babies were going to be hurt or even killed by mom if I left them in with her.
I covered some mom and baby care in this old thread if you want to take a look. It also has a picture of what a full belly will look like.
http://www.rabbitsonline.net/showthread.php?p=1055673#post1055673
And this link has some helpful tips as well.
http://flashsplace.webs.com/accidentallitters.htm