Matches are playing a certain number of games against an individual repeatedly, not tournaments. It's to prevent people playing a bunch of matches to get a lot of points.
Question about maximum USCF rating change.

Hmmm...that sounds bad.
Already, I think the provisional rating is too important...I feel like people that just start playing rated matches without knowing what they are doing and get a low rating to start with end up climbing a long hill compared to people that get good while unrated, then start playing rated matches and nursing their provisional rating along.
This is much similar to the ratings on the tactics trainer...if a person just starts using it like a set of fun puzzles, they will get a bad rating by not reazling that "trying" moves and then resstarting hurts them, walking away and making a sandwich hurts them, etc. They may assume that correct solutions are always positive when the comparison of average time spent makes this not the case.
I also think the rating systems (FIDE, UCSF, here, etc.) need stronger incentives to mix things up. People lose too much by playing below their level and so avoid it. Draws are worth half a win; perhaps wins should be 3 pts, draws 1 pt. like in many sports. Ratings do not decay as far as I know, so someone can nurse themselves to a high rating and become petrified of losing it and retire ;). There's a lot of inflation control built in, but it seems to have a negative effect on players, not a positive one...and it doesn't work anyway, as online chess sites like this one show.
If people are able to play mountains more rated games, they will naturally go up to ratings that eclipse FIDE ratings...you can't artificially stop that from happening. Chess ratings are not a closed system...you have people entering and exiting all the time, but far more low rated players enter and exit the system than high rated players, feeding in points as they lose and then exit.

Ratings come and ratings go. I'd worry more about winning those two games.
Every time I start to worry about a rating injustice ("That guy was at least 300 points under-rated!"), I remember that after another twenty games or so, what happened in this one will be completely irrelevant. If your rating goes down from one game (or doesn't go up enough), that just makes it easier to gain points later.

I'm just here to clarify since this is 7 years old and something may have changed
Tonight I'm playing a 1991, if I 2 - 0 him I will gain 57 pts on the rating estimator. But since it is a match will I only get 50? And is it morally unsound to rate it as a normal event for 7 pts? (Those 7 points would put my rating above 1800, otherwise I'd be a 1794. Only reason I ask)
Yes, 50 points in a match is still the maximum. If it is the only get submitted, it likely will be still rated as a match.
I read this about USCF ratings and was confused:
The maximum rating change in a match is 50 points; the maximum net rating change in 180 days due to match play is 100 points; and the maximum net rating change in 3 years due to match play is 200 points.
I do not understand this, as my rating has changed more than 100 points in 180 days and certainly more than 200 in 3 years, and I am not a provisional.