Bell's Expedition Stout Help

Many who have tried Bell's Expedition Stout would agree it's a phenomenal beer. Unfortunately, they don't distribute near me. Fortunately, I have greatly enjoyed brewing over the last year. I found the recipe below posted supposedly taken from a 2003 issue of Zymurgy. I'm hoping to brew it in a few weeks. I fully recognize this beast is going to take some time to condition. What I'm trying to figure out is the following:
1) why would they use amber dme? I heard it's because they didn't originally have room for all the grain.
2) when I emailed the brewery, the one guy (in the homebrew supply store attached to the brewery) said the grain bill looks pretty good, but might take out some base grain and add about 2# of Dark DME? Any idea why that might be the case?
3) When I calculate the grain bill even as listed, it's way above the 1.110 OG with (10.5 %abv), I was thinking about a starting gravity of 1.126 with a final gravity of 1.026. Does that work for a RIS? Mash at 150 or 152?
4) I plan on using a yeast cake of the San Diego Super Yeast from White Labs after brewing a holiday beer.

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Bell's Expedition Stout Clone
Target OG 1.110
Target IBU 100

23 lb. pale 2-row
1.0 lb. flaked barley
1.5 lb. roasted barley
1.0 lb. black patent
1.0 lb crystal 80
0.5 lb. chocolate malt
3.3 lb. amber malt extract

2.5 oz. Centennial hops 10% AA - 45 minutes
1.5 oz. Centennial hops 10% AA - 30 minutes
0.5 oz. Centennial hops 10% AA - end of boil

Single step infusion mash @ 150-152 deg. F.
Collect as much wort as practical - reduce volume to approximately 5.5 gallons by extended boiling. Add extract to the wort at the beginning of the boil.

For my next brew I too am planning an (russian) imperial stout like Bell's and have similar questions.

If I end up doing what you have listed above, I will probably leave out the amber malt. I don't know about the dark dme either. For me, mashing 28 lbs of grain is a ton already and will get me the biggest gravity - hopefully 1.100+ . I think 150-152 is a good temp target.

I don't like extended boiling (it just makes the brew day take that much longer), I've done the math and I'm better off just adding more base malt to get my numbers rather than burn propane.

I'll be pitching onto a pacman yeast cake from a pale ale (that I made yesterday). The super yeast cake sounds just as good.

There is a RIS recipe on here that I might make instead.

I'm with you in terms of extended boil time and using more grain. I'll pay the extra few bucks to use more grain at lower efficiency. I'm just not sure what the amber DME was in place of in terms of grain. If we take that out, should we add something else (vienna, munich, dark crystal, special b, etc.)?