False Pregnancy Possible in Rabbits (Flemish Giant and mixes), What Flea Products are safe to use on Rabbits?

Hi
I have three rabbits, one flemish giant, one flemish giant/champagne mix, one flemish giant/mixed with a small rabbit. They are all very loving, sweet active and healthy. My problem is that one tends to bite the other two rabbits, when she's around food and sometimes most recently she'll just chase and bite them for no reason.
The other issue I have, is that I'm not sure if one is a male because the two older females(one had a litter of mixed babies and I have one of her babies too but she doesn't treat her like its her baby). The baby may be a male(buck) but I'm not sure and need some help in identifying. They all started pulling hair and making a nest in my couch and was wondering if its possible that they think they are pregnant because even the females will hump each other. Do rabbits have false pregnancies?

I noticed the rabbits all started itching and found a flea on one of them. What is safe to use on rabbits to get rid of fleas and what is safe to use/treat the house. They have a tendency to eat my carpet and walls because they are all so big that I do not have a cage big enough for them and they free roam my home. Yes, it is difficult to keep anything from being chewed on and a lot of poop/urine to clean but my main concerns are safe treatments for fleas and possible false pregnancies in rabbits?

If anyone knows or has had this happen to them, please let me know and any types of suggestions are welcome. Thank you and love your rabbits, they are wonderful, loving pets with great personalities!!

Thank you all!!