What sort of time limit?
Turn limit rather than time limit.
2 options are a Piquet style moving clock. Allow an hour on the "clock" and at the end of each turn roll a d6, on a 6 (or 5 or 6 if you want) the clock moves on 1/4 hour, reach the hour and the game ends. Or a Peter Pig style countdown. Start at 21 and end of each turn roll a d6 and deduct that score from 21, reach 0 and game ends.
As for treasure, take one away rather than add an extra, there is already the potential for too much money in the game with 6 treasure.