I came out ok with mine that were booked ahead of time. I did move from a 3pm Acela to a 2pm Acela in Sunday.
Arriving Union Station at 1:51pm (assuming it is on-time) is a pretty tight connection to make the 2:00pm Acela. Amtrak might even close boarding at 1:55pm. There is no margin for error. Miss that Acela, and you're booking a walk-up fare for the next one at 4:00pm, or walk-up on a Regional. You might want to consider the 4:00pm Acela (#2220), or leaving lunch a little early to catch an earlier set of Metro's back to Union Station.
I'm on the 4:00pm Acela.
Leaving Tyson's Corner at 12:57 arrives Union Staton 1:41.
Also - we won't know about WMATA trackwork for next weekend until early in the week; most likely on Monday.
Ross