I've never 'done' Facebook personally (have written stuff for Dreamworlds for the site's 'presence' but somebody else had to put it up for me as I find it totally confusing). The more I hear about it the more I'm repelled with people you've never heard of 'friending' you when you more than likely wouldn't ever go near them in 'real life' - far too few barriers and too much exposure which I know you can 'grade' but if you have to do that then why are you there in the 1st place.
It's a very simple thing to say ' I have to move on', but bloody difficult to do so, even if you want to do that very much indeed. I can see how you'd need to try for some closure with this disgusting man, but I'm glad you're questioning getting in touch with his daughter. If you're right about her then she most likely was as much a victim as you were, maybe more so. He's gone now and hopefully to a 'reward' that befits the nightmare he put you through and any others caught up in his obscenities.
Although it's still stuck in your head, you have already moved on somewhat. Had children and grandkids? Married people you loved for a time at least? And now you have a life where people cherish and think highly of you in real life and online
You're ill yes, but you've also achieved a lot and shown that you're strong, intelligent and indomitable - a fighter not a loser even if your health, mental and physical can lay you low sometimes, your spirit is magnificent hon (((have some more hugs)))
Dump where and when you can Tina as much as you need, but I think you should try to resist contacting this lady in Maryland, stay well away from her. Her father ruined enough lives already and he's gone now. Leave her be and there'll no more additional ashes for you to rake over. Don't let her memory of him haunt you as well because you might end up sharing her nightmare as well. It's truly not worth a second more of your time or effort.
Revenge as in the movies is not a positive, nourishing thing - you already got your revenge by living a full and significant, rip-roaring life!
Don't let him keep on abusing you in retrospect. Easy said I know, but I think you already know that you could keep on destroying yourself inside if you can't draw a line now.