1) prepare yourself to leave the job: save money, dedicate time to search for jobs, update resume, etc.
2) Write note summarizing the hours you put in, what your roles are, and how the pay cut is disappointing.
3) Practice a conversation with your boss expressing what you have written w/o getting emotional or angry. Just an informative talk. Prepare to give him a chance to respond.
4) Have conversation, give him note, verbally inform him that you will only be working on your responsibilities while in the office. The other time is to find a job. Do not verbalize this to him, he will figure it out and probably ask you about it. Have a response ready that is on the line of 'the cut in pay effects my personal life and expenses.' You do not want to directly say you are looking for another job.
5) Hand him note and send same note to his boss or human resources. If he is the top of the food chain, perfect.
6) Spend the time you would be working to find a job.
7) If he reconsiders his pay cut, have followup conversation that the trust had been damaged. Ask him to fix the situation.
8) Leave unless he goes above and beyond to fix trust.