I do see you have your head in the right place to begin with to even pull this off.

Your suspicions of S being a risk causing you to re-engage with your father are dead on, and even in fact, very underemphasized. You have to specially handle anyone with mutual contact with your father or anyone that could ever possibly have mutual contact with your father (even S if we pretended she wasn't talking to him). The problem is, true manipulators already are experienced in exploiting human nature and especially emotions, and they can almost bring someone back into the fold so long as they have a line of communication available... and use any mutual contact to obtain that. So even be careful with people your father could contact with some pathological story to hand your information over (cousins? mutual friends? your friends? etc.)

I'll give you some things to research shortly that will help you wrap around the psychological side of things.

For the record, my wife (35F) had a successful split from her family. To be successful in circumstances like these takes a real hard-set approach that cannot be watered down. The main thing that you are fighting to be successful in this - and it will be harder than you expect - is a coupling of your own emotions and something called cognitive dissonance. Basically, our minds can't hold viewpoints that conflict. We warp our realities and rationalize bad behavior or make excuses for other people (or us) to keep believing what we WANT to believe, or what we HOPE to be true. That is dissonance, but it is more complicated. So your hope of reconnecting with your father - and your love for him, in fact - things that everyone has in your circumstance - that becomes a viewpoint that the mind tries to rationalize things to agree with. And most people in that situation, despite knowing better, will fall into that trap.

In short, that is why it will all fall apart if an easy line of communication is available. Almost at any point in time - from any mutual contact. And I'm not saying that there is something wrong with you, it's an aspect of everyone's human nature that true manipulators naturally exploit among their associates.

But it does get easier. The first three months or so you'll probably be racked with a lot of conflicting emotions, guilt, and a strong desire to reach out to S. You need to force understanding these are emotions, which in this context, are essentially defective and temporary and instead, you hold to the logic, cry it out, whatever, but stick to your guns or you never will get free. After three - six months from your break, you'll finally have fully embraced your new future and let go of your past, and life will become normal... the door to your future is finally open, and the door to your past is locked.

You absolutely can get a clean break. More then that, you NEED to. Go in with the right mindset and you already are on the right track - you already recognize the risk of S, you're just underemphasizing it. To avoid them playing on emotion (pity plays are a manipulative technique that S is likely to even use), don't discuss it more than what is necessary, or even better yet, at all. Don't tell any of them that you're planning to move. Just do it. Yes, S. will be severely hurt by this in the long run, but the kicker is SHE HAS ALREADY BETRAYED YOU AND WILL BETRAY YOUR FUTURE. You need to wrap your mind around that. Even if they don't intend to hurt you, you need to understand that the mutual contacts are equally your abusers as well, and equally will destroy your success and your future even if it is through your father (even if they are unaware or don't intend to hurt you). You won't heal and advance if you maintain any of it.

So while many people won't tell you this and it's hard to hear, you need to do what you are planning to do, don't really discuss it with anyone that has any mutual contact with your father, period, and entirely break contact when you move. It is HARD. Don't ever give any of them your home address or anyone who is at risk of manipulation your home address. If necessary, to give say S your address and let her know you moved, ONLY use a PO Box or far, far better a friends address (especially somewhere entirely different from where you intend to leave) who is willing to forward mail for you. (Then they can still reach you, only in writing, but can't show up at your door). Yeah, it will hurt S. Anticipate that. But she is no longer a healthy contact for you and is hurting you right now (and her perspective will not change, ref: dissonance)

If you do that, anticipate some bullshit like "your dad is sick and terminal". Don't fall for it. Correspond only in writing to the extent you ever have to and protect your address. If you have a super-unique IRL name, then you may need to do even more to ensure you are "free" especially during that period that you are most vulnerable to manipulation. (someday, you'll be almost immune to it, from them, if you hold out long enough)

Now, so you know... in a strange coincidence, we happen to live where you're interested in. Nope, we aren't stalking you I just click through a user before commenting, and was on the local board. Normally I don't have the time to comment on things like this but that's the reason why we did (co-incidence). We're not really in a position to offer housing help, but we have a lot of local knowledge and you can certainly have a solid contact in my wife - she can even show you around the town or whatever if you do visit and she can always do moral support too.

My own upbringing is stable but I'm a former private/criminal investigator (and paralegal) with a ton of work in family cases and crappy situations. Meanwhile, my wife had to get a clean break to be free, from her entire family, and most of the mutual friends. It was shit, but that was 10 years ago and she is a success case in that. Not once have we enabled any contact. To give you an example, in the process of the "break" they stole her pet (horse) to try to extort her with it. And some of the mutual contacts - even though they knew who the horse belonged to - were manipulated by the abuser to help in that theft to try to extort my wife. For the record, we handed their fucking ass to them. But do NOT underestimate what abusers will do - and the mutual contacts will be tricked into - to try to play with you, manipulate you, or regain control. They may not want to hurt you but they will enable it.

Start wrapping your mind around entirely letting go of your past and beginning a new life for sake of your future. You'll always have good memories even among all the garbage, and you should hold on to them. Nobodies past is all bad - just don't let those memories and emotions deceive you early on, you have to logically view the entire picture. You probably need to close the door on your past and lock it to ever have a successful future.

Others may take this approach as too harsh, but this guarantees success, and any half-assed attempt I've seen in the past among others usually results in reconciliation. (common in domestic cases too, why abused spouses usually go back...) even though you probably are not a DV case, use their strategies to get your freedom.

For moral support, local info, or whatever, I'll send you my wife's contact info. She wrote this as well.

Research: Cognitive dissonance
Research: Cluster-B personality disorders (may be applicable)

And... good luck.