What should I do after my husband said he hates me and wants a divorce because I didn't want to go to an event with him to promote his painting?
You really want to speak to your pastor about this—and very soon. He is in a position to listen to you (and your husband) explain what happened and then counsel you on the basis of God’s word.
If, for whatever reason, speaking with your pastor cannot take place soon, you could consider another resource. Christian Family Solutions, an agency within WELS, offers counseling: both in-person and video counseling from the privacy of your home. This link will provide you with more information.
Communication is vitally important at this point. I pray that you and your husband are able to exercise patience, wisdom and love as you address some very serious matters. God bless you.