If you had not thrown more than 30, your coach should not have used you for much more than that number.
The problem with most short bus riding coaches is they think you can get loose a couple of times a week and you will be good to go come game time.
You must practice what you intend to perform. I would not be out there throwing 70 pitches in a game until I could throw at least 60 in a bullpen. (understand that bullpens will be a series of 10-20 pitch sets with 3-5 minutes of rest between sets)
This is how I prepare my pitchers and no arm strength issues at all. Some kids just can't throw that many pitches at one time. There is nothing wrong with that either. These will just not be the starters. Only the kids who can give 65-85+ pitches can start.
Don't let your coach do this stuff to you again. Take some ownership to get ready in the off-season if you know your coach is a DBag.