I have a question about the 3 minute break before the match tie break set. If you need to use the bathroom, is that time included in the 3 minutes? The rules state you can go to the bathroom at any time, but it is preferred to go in between sets. Some clubs have courts far away from the bathrooms, or they have only a few bathrooms, so you have to wait in line which ends up being more than 3 minutes.
Bathroom breaks are really a separate issue. The break between 2nd and 3rd sets of 3 minutes is designed to give teams time to get a drink, towel off and then confer with their partners and regroup before playing the tiebreak for the 3rd set. That would be the time allowed when all players remain on court and are ready to play the tiebreak. As you say, the rules allow for a bathroom break at any time. Those breaks are not defined in terms of time allowed because, as you say, every facility is different. So if a team chooses to take a bathroom break between the 2nd set and the tiebreak, then the bathroom break should be completed as promptly as possible and then play would begin as soon as they returned to court, assuming the 3 minutes were already up. My suggestion would be that in most cases I don't think a bathroom break should be necessary at that time since there is only a tiebreak left to play. I know teams have gotten in the habit of taking a bathroom break between 2nd and 3rd sets, when we had the 10 minute break, and when there was still an entire set left to play. But with just a tiebreak left to play, I would think most players could delay using the bathroom until the tiebreak is over. That being said, a bathroom break is allowed at any time and if players need to use the bathroom after the 2nd set they may do so.
4 person(s) had a similar situation.