Yes it makes sense. No, I don't think it's too long or difficult to understand. Small changes I would make.
"But when his dad sat on the couch that night, took the first bite and said, “Outstanding! The best brownie ever!”, Howie beamed with pride."
You don't need to include 'down' as it's implied when saying 'sat'.
I feel saying 'beamed with pride' is more natural than saying 'never looked prouder'. Either would work though.
Not a teacher....Yet
Student or Learner