Just read your post and registered just to reply!
Truth is, you CAN"T pretend he never told you this. It's "out there" now, and needs to be addressed. Your husband was obviously going through a great deal of inner turmoil over his mothers' illness and the past to suddenly blurt this out. To try to avoid it now will only compound the problem.
You can't force your husband to go to a therapist. I've been married over 20 yrs. I knew about the abuse shortly after our marriage, and my husband denied it's impact on his life and our marriage until just last year. It's been quite a roller coaster emotionally and has almost torn us apart, but he is working really hard on recovery.
You're on the right track, you're here, you are trying to learn and seek support.Check into some therapists in your area to see if theres' someone who deals with these issues. Gently mention if you've found someone. Until he's ready, arm yourself with knowledge and give him your love and support. God bless