I'm not sure which price/night that is but courtyard is listed with 270 and 295. lets use the 295.
295X10 nights + tax = 3289.25
so the total now becomes about 5340 add insurance and that is probably about the DU quote. (270 a night would total about 5060)
AAA discount is 15% i think off your hotel (or hotel portion of a package) so your hotel price would be 250/night or about 2796 with tax for 10 nights giving a total of about 4845 again add insurance and that should be pretty close to their quote. (270 a night would be about 4608)
So it looks like they have given you the AAA discount. Technically you are supposed to be a AAA member to get that price but it has been discussed on the boards in the past that if you book a AAA room only through DISNEY they do check but if it is a AAA package through AAA they dont. I think the assumption was that if aaa is going to book you a package they are going to make sure you are a member before helping you. Which isnt always the case. But my AAA wouldnt even talk with me till i bought the membership. and it would suck to get there and not have a card to show and them want you to make up the extra 500.
They should be able to add any future discounts to your reservation but it would basically (usually but not always) be which deal is better not an extra discount on top of what you have. Not all travel agents are willing to go through the trouble and I dont know about change fees and stuff. My agent made it pretty clear that once I booked she was done. Since I was only using her for the discount and last minute at that I was fine with it and didnt have reason to find out if she really wouldnt help out if there was a new discount.