I don't know what you are calling "charm". The Bible says "charm is deceitful. . ." (Proverbs 31:30) but there's no reason that "normal" men can't be pleasant, witty, etc. which is a lot of charm. I'd look at what you are meaning by charm, whether he is getting or avoiding something with his charm. I'm charming and trying to change that aspect as I use my charm to keep from having to work very hard at things I don't like and to get out of "scrapes". I think I'd say the opposite of charm is directness, admitting faults and worries.

An acid test might be to ask him what HE thinks of his abusive past and see how he handles the conversation. If he is not "worried" that he may act abusively again, then run. I didn't have children partly because of my stepmother's excellent training in how to be abusive and because I was afraid I'd be angry and verbally/emotionally abusive too often. I might do fine now and don't particularly worry about being with my husband's grandchildren but I've had 18 years of therapy.