The Spurs aren't choking any more than any other team has that had a game 7. You could argue that OKC had more choke moments than we did, because the Grizz pinned them against the wall multiple times, but they came together when they had to the most in the last game of the series. , the same goes for the Pacers who were playing the worst basketball in the whole playoffs despite being the top seed in the East, and they came together in the end; the Spurs are more than capable of doing the same.
The Mavs are a good team that were in desperate mode the past 2 months of the season while we mostly cruised, despite our win streak. I don't really think it's a true "choke job" if we lose the series, although it sounds like it at first. An 8th seed beating a 1st seed sounds improbable until you realize that the gap between the teams in the West isn't nearly as severe as the East. All of the teams in the league have struggled in round 1, excluding the Wizards and the Heat.
I can't guarantee we'll win the game, because these playoffs have shown that anything can happen at any time. You just need to have some faith in our team, game 7's at home is why you fight so hard for the top seed in the regular season.