1) What are the signs telling me that she is pregnant?
Firstly that she is getting bigger around her stomach Her attitude might change and she may be more stand-offish or defensive, but not all does are this way.
2) If she is, what kind of nesting box should I have for her?
Wooden is preferable. Though plastic works too. It needs to be big enough for her to stand in and turn around in without stepping on kits. Three of the sides should be quite high, with one side a little lower (but not too low so that kits can crawl out, they’re surprisingly mobile from a young age). Keep bar spacing on your cage in mind, they can easily fall through cage bars if they crawl out of the nest and become too exposed and die.
3) What do I do if she takes care of them?
If she takes care of them you won’t need to do much. Check that she’s feeding them, she’ll only do so once or twice a day in early morning or late evening. The bellies after a feeding will look round like ping pong balls. If they’re wrinkly and not rounded, chances are they haven’t been fed. Also check the nest box to make sure it isn’t getting too soiled, don’t remove the whole nest, but you can spot clean small parts of the nest if needed to keep it relatively clean. Also, if she’s used to veggies and things, feeding her kale is good because it’s high in calcium and should help with her milk production. Don’t feed lavender as it’s bad for pregnant does.
4) Do the female and male have to be separated now?
Yes, 100%. Not only could they get into fights, especially with the doe protecting her ktis. But he could get her pregnant the same day she gives birth. Separate them ASAP and make sure that there is a gap between their cages, as rabbits are known to mate through cage bars/wire.
5) I am worried that if she does give birth when I am not around that she will die and I don’t want that, so how do I prevent that?
Death is certainly a risk, though most come through it ok. As mentioned, she’ll usually start pulling fur to make a nest either the day before she gives birth, or right before she gives birth. So definitely keep an eye out for that. To my knowledge most give birth overnight, so make sure you have the contact details of a rabbit savvy emergency vet on hand in case you need to take her in if you think a kit is stuck or something isn’t right.
6) How old do they have to be until I fix them? and is it important to do so?
With the doe, you will have to wait until after the kits have been weaned and separated from her (8 weeks). Your buck can be done at any time, the kits from around 12 weeks depending on your vet. Though all the kits will need to be separated from each other by 10 weeks of age to prevent further breeding. If you want to house your buck and doe together as a bonded pair, they will both need to be spayed/neutered before you can attempt to bond them. The same goes for any kits you decide to keep. It is not recommended to keep intact rabbits together, not only for breeding between m/f pairs, but also due to fighting between f/f and m/m pairs. As mentioned, the risk of uterine cancer in intact female rabbits is very high.