Yes, Tennant modeled his character after Peter Davidson, and Matt Smith after Troughton.
Capaldi when he was announced did the hands on his lapels like Hartnel used to do all the time when he was thinking and being triumphant. I hope that is not just me reading into things, but a sign that Capaldi is looking to Hartnell for inspiration. I would be pleased.
I had known about Smith and Troughton. Smith even modeled his costume after Troughton's with the bowtie. A throwback to Hartnell would be fun especially considering that Capaldi is the first old guy to the play the Doctor for quite some time.
I feel like it would have been way stronger if Tennant and Smith had to come to terms with their actions by pressing the button. It would have been way more satisfying to me if we had seen The Doctor(s) stick to his/their original decision and face the fact that, sadly, people have to die sometimes. I know he has dealt with that problem before, but I would have rather seen him face the reality of being completely alone with no other timelords being in any other universe, like Tennant had to deal with when the Master died. It seems like that's what they've been going for with the reboot. They bring up his loneliness a lot, so I figured they'd want to keep that a motif.
Other than that, I loved the special and everyone's interaction in it. I only had a problem with the ending. Now I want to see more of John Hurt. Can't we get a War Doctor miniseries?
I was okay with the Gallifrey retcon partly because it is consistent with how time has been working since series 4. In the Library two parter we are presented with what looks like a fixed point that results in River's death, but in that same set of episodes we learned that the Doctor had been thinking of a way to save River for years. It is because of the older Doctor thinking of a way to save her, that she got uploaded into the computer. In a way, she still died and the fixed point was satisfied, but the Doctor still managed to get a happy ending of sorts.
We see this again in the finale to the seventh series. Again, the Doctor's death is supposed to be a fixed point in time, but he manages to cheat it in a way that the event still happens, just not the way everyone thinks it does.
The resolution with what happened to Gallifrey is actually very consistent with what the show's been doing. The Doctor has become very good at getting around hopeless fixed points in time, and he does it in a way that fixed point is satisfied, but the result ends up being slightly different from what was expected or originally thought.
And anyway, Fixed Point makes everything indestructible, right? ;)