Aack..the 20's..luckily I am finished with them...your pondering "what to do and how to do it" brings back memories.
First off, if the email was threatening, you need to print it and keep it. You may need it. Secondly, get the drama OUT of your life. Put the guy on block or whatever you need to do.
Last, keep your eye on the ball. If it is a career and good life you want then keep moving towards it. No matter what. Don't let miserable people with little ideas and big drama get in your way. Walk through it/them and keep on going.
Are there meetup groups in your area for others in your profession? Have you ever been to Toastmasters? What about doing volunteer work for Habitat for Humanity or Meals on Wheels or whatever? Often times, these things bring out the best in us. While we are exuding our best, it's the PERFECT time to attract others like us!
Good luck!