i have a similar setup to you and also had to adapt to the 3d-xl situation so i can answer some of these:
1. i have the hd66/3d-xl combination and i haven't researched all the dlp options, but i would recommend the highest level of contrast and brightness possible, and i think the hd66 tops it out or is among the best. i've seen the optoma gt "gametime" series and they leave a lot to be left desired in 3d mode, and the 3d menu system on those models are clunky. i'm very happy with the hd66 though...in 3d mode, in regular mode the rainbow effect is very present on mine, but it's virtually non-existant in 3d. so i'm running a dual projector setup, an old 1080p epson sitting on a shelf 21 ft back for anything 2d, and the hd66 for anything 3d
2. i have 3 zd101s and 4 ultra clear dlp glasses. i have to say the zd101s are definitely the better pair, the color is more accurate, contrast is better and more light gets through, BUT they are significantly heavier and take 2 batteries each and estimated to not last as long. they have ZERO ghosting on this setup and rarely fall out of sync. it almost completely blocks out the dlp-link flash, but the "shuttering" is more sensitive to the eyes so it may cause the eyes to strain more...this is hard to explain but you'll be able to know the difference after some experience, i think it is due to the eyes trying to accomodate from completely black to completely clear repetitively so fast so while it looks better it might be a catch 22. also for a 2 hour movie the zd101s might be good, but any more than that (like a 4hr or more gaming session it will really wear on your nose, perhaps making it stretched or longer). probably a temporary effect but still something to consider. the ultraclears aren't as good in that the contrast is less probably because the shutters aren't closed for probably as long, but the eye strain effect i'm talking about is a lot less and very comfortable. the color is also a bit tinted but maybe this can be accounted for in the color settings in the projector. they are very comfortable to wear cuz they are light and are not bothersome after any time. HOWEVER there is a very slight buzz that can be heard when you wear them...but that's only when things are totally silent and you're trying to hear it...but it's definitely there. i'm glad to have both to choose from (and vary which one i'm gonna wear), but if the visuals aren't super important and i'm not concentrating on them (like if i'm just playing a game/chatting with friends online instead of watching a high integrity movie), then i'd go with the ultra clears. if i'm watching a 2 hr or less movie i'd go with the optomas. also the optomas have bigger lenses so they are better for the seats closer to the screen.
3. i'm not sure if your cables will pass 3d, but they most likely will. only ONE cable that i have refused to do it (which i wasn't even using), and my pre-existing 1080p cables worked perfectly (and they were cheapo ones i got from amazon). however the 2 dollar six foot ones on amazon will probably not work, but people in the reviews of those state problems with 1080p sometimes. if you setup runs in 1080p without any glitches then they probably will work i think. HOWEVER, i have a 50 ft hdmi cable i got from amazon that runs to my 1080p 2d projector in the back, and this did NOT work directly connected to the hd66, if you check the review on projectorcentral.com they said that the hd66 was unreliable with cables at that length but 25 ft ones worked. however for me and probably you this is not a problem because they way i have it, i have the 50ft cable going to my 1080p, but i also have the 3d xl on a shelf right under it, so when i want to watch 3d i just take the cable out of the projector and hook it up to the 3d-xl, which then works as a repeater/amplifier and then i have a 20 ft cable going to the hd66 mounted on the ceiling. i'm sure you could get an hdmi switch so you wouldn't have to take the cables out and just instead press a button, but this works for me as i also have a 3d blu ray player back there hooked up to the other input on the 3d-xl since my receiver is 1.3 and can't handle a 1.4 1080p signal. i have an optical going from the back to the front receiver...no lossless audio or 7.1 but it works without having to upgrade the receiver. you should be fine though with your 1.4 reciever, i also have a ps3 up in front by the reciever and 3d games work great through it even thought it is 1.3 because the box can pass through 720p 3d, but blacks out on 1080p 3d. so i only switch the cable when i want to play 3d games.
4. the hd66 with absolutely NOT fit the screen from that distance back. check projectorcentral.com distance calculator (or the one on optomausa.com which uses the same flash thing) to get the correct distance you need). i had to ceiling mount the projector about 16 ft back from my 135" elite screen fixed frame and run the cables through the walls...luckily enough i was about to do this without much trouble. the zoom on the hd66 is very limited and i think that's the case for most projectors in this pricerange, if they have zoom at all. i'm thinking you'll have to mount it maybe 15' or so back from the screen but i'm not sure. also the hd66 is an "on the floor or on the ceiling" projector, and can't be pointed straight directly at the middle of the screen because it shoots the image way above it. i have it about 6 inches from the ceiling and it's still pointing up a bit even though the top of the screen is more than a foot below the ceiling. i got the metal hd66 mount on amazon, not sure which one, but it wasn't the cheapest, and it's really good and sturdy. it's about 30 dollars i think from a company called "projector mounts direct" or something.
5. i also have dish network but i have a regular box that doesn't do 3d, and they don't have any 3d channels unfortunately. i think the new expensive box has 3d on demand but i have no experience with that. however on the ps3, the 3d movies from the playstation video store and also stream from vudu work great
anyway once you get it all hooked up i'm sure you'll be happy with it, and btw tangled is going to absolutely bring down the house, it looks incredible!!