When to give up on marriage?

After years of discord and struggle, I decided to leave my ADHD marriage. When I informed my ADHD husband, he insisted he would do anything to "keep our family together." As an example, he explained that we fight because I'm too controlling and he needs to assert his individuality. He offered to "give up his individuality" if it meant I would stay. In the days since I said I was leaving, he's been Mr. Perfect - home on time, brings flowers, no major conflicts. After years of riding this roller-coaster of a relationship, I don't believe he can sustain this focus on our relationship.  Now, I feel incredibly guilty for leaving, yet I can't bear the thought of staying in this relationship. 

Some history - Early in our relationship, my husband's ADHD symptoms made him seem fun and spontaneous. When we had a baby, he was of little help, and our relationship deteriorated rapidly. I dragged him to marriage counseling and got his ADHD diagnosed. He insisted it was just his "personality," and we abandoned both marriage counseling and him getting treatment for his ADHD. He lost his job and made little effort to find a new job, living in denial while I stressed over both the baby and our finances. He finally got a new job, we moved to a new city (with me managing the entire move), and I was left a weeping wreck. In the last six months, he has made significant improvement in parenting, taking on some responsibilities and being home more. However, our relationship has been strained at best. We rarely converse except about our child, sleep in separate rooms, and argued when we did interact. I no longer trust, respect, or love my husband. I decided it was time to move on with my life, but he's desperate to maintain the illusion of our happy marriage. Now, I feel overwhelming guilt that makes me hesitant to leave, yet I don't believe I can ever be happy in this marriage again. I could really use some input from those who have been at this point.