Question re: baby rats

Question
I rescued a female pet rat from a military family that was moving about 2 months ago. They assured me that her male cagemate was fixed, and it sure looked like it to me. However, just last night, I discovered two baby rats, both already furred, eyes open, alert and ears open, coming out of the hutch (which I never move, since the new rat, the mother had gotten very protective of the hutch, for now obvious reasons). My other rats are all females, according to my personal sexing, the vets and previous owners.

I have multiple questions.
1. How can I tell how old the babies are?
2. Is it possible for a supposedly fixed male to have a "slip up" and impregnate a female?
3. How long until I can sex them?
4. How can I change the bedding in the hutch, now that that I know there are babies?
5. Is it possible that there were more babies, but the mother ate them or killed them? I did a quick inspection for corpses but didn't find any.

They all have a vet appointment this week, but not until Thursday, so if any of my questions can be answered before then, I would be much obliged! Thank you in advanced!

Answer
1. How can I tell how old the babies are?

Here is the perfect site to use as a reference:

http://www.evergreenrattery.com/careguide/baby_development.html

2. Is it possible for a supposedly fixed male to have a "slip up" and impregnate a female?  

****Not that I have ever heard of.  However, the key word is "supposedly fixed"   which means, are you sure he was indeed fixed?

3. How long until I can sex them?  

** Experts can do it the day they are born.  Its not as easy for a less experience rat enthusiast, however, but here is a good site to use for reference.

http://www.evergreenrattery.com/careguide/sexing.html

4. How can I change the bedding in the hutch, now that that I know there are babies?  

**Do one side and simply move the pups and mom for a brief moment and change the side they are on.

5. Is it possible that there were more babies, but the mother ate them or killed them? I did a quick inspection for corpses but didn't find any.

***If the pups died for some reason, there usually wont be any corpse. Mom eats the entire pup. Yeah....I know.... yuck.  However, if that male is in the cage, he will indeed kill and dispose of them. Male rats, intact or not, will kill pups under 6 weeks of age.  He can also get the girls pregnant, including mom rat.  Mom rat is fertile the day she gives birth.  They do not stop ovulation just because they are nursing.  
Increase moms protein and iron by giving her either soy baby formula or soy milk. Also a nice scrambled egg daily is a good boost for her protein and iron intake to replace what the pups are taking from her.



*********

You should also be handling the pups daily to get them social. If you do not, they will be almost like wild rats, not used to humans, wont allow you to touch or pet them etc....they will be very antisocial and difficult to handle.  If you plan on finding homes for them, it will be hard to place them because they will fear humans and wont want to interact.  Mother rat will absolutely NOT hurt her babies if humans touch them. In fact, she will appreciate the break!

Also, hopefully you have taken the male rat out of the cage. Even if he is fixed, he will certainly kill the pups. Male rats kill pups under 5 weeks of age, fixed or not.   He also needs to have a test to see if he is indeed fertile.  If he is, you need to have a good talk with the people that gave him to you!!!!!