spendysis it depends what you need from therapy. There's many different kinds. I'd look into some to get an idea of what they're about and see if you feel drawn to anything in particular.
I guess because our situations are complicated, I'd go for someone properly qualified, so a psychotherapist at minimum (they've done a psychology degree plus something else, I think). A psychologist is higher qualified still and they're doctors, just not the drug-prescribing kind (for that you need a psychiatrist). A lot of counsellors and CBT therapists aren't very qualified, but this doesn't mean they can't be or that those types of therapy aren't worth it.
Core beliefs CBT could be useful for pulling apart things like feeling bad for walking away and helping you realise that protecting yourself from harm isn't bad, but necessary. Someone properly trained delivering core beliefs CBT is on another level from someone who has done a week-long course in negative thoughts patterns and how to avoid falling into the trap of them so they can deliver a few very basic CBT sessions to people who have nothing much wrong, apart from being glass-half-empty types. Obviously that basic knowledge is helpful and underpins CBT, but with these complex family dynamics we probably will always need to dive deeper.
EMDR is good for processing traumatic events.
Art therapy is good especially if you find it hard to express yourself with words, you don't need to be any kind of artist it's not about the creativity itself, it's about using creativity to express yourself and learn about yourself in the process.
DBT is good for people who can't regulate themselves emotionally.
Counselling can be useful if you just need to off-load or to figure a few things out.
There's other types too. All types of therapy are good for helping you "unstuck" yourself when you don't know how to go forward, IMO. Various forms of therapy can help you learn coping strategies for dealing with overwhelming feelings, depression, anger, or anxiety and panic, in an emotionally healthy way.
I think of therapies like painkillers, there's not one painkiller for this condition and another for that one, it's not that simple. Many painkillers can help a variety of conditions and sometimes, in your own particular case, a painkiller that works for lots of others just won't work for you and you'll need to try something different. Same with therapy and the therapists themselves. If something/someone isn't helping, don't give up.
The main thing is to find someone who accepts that reuniting with family isn't what's being worked on, those therapists will keep you stuck in the loop of pointlessly banging your head against the "wall" (your FOO) and that's really something that's down to the individual therapist. You don't want to be wasting sessions feeling like you're justifying or proving to the therapist why that option isn't an option for you. Explaining the situation and background is one thing, feeling like you're having to convince them not to repeatedly try to steer you down that road is another thing entirely. It's just a waste of your time and money and an unnecessary pressure on you, when you're already dealing with so much that you've ended up in therapy.
I'd rather work with a less qualified individual or someone with fewer skills to help me, but with the right attitude to support me in my choices, than with someone who really does know it all psychologically but who believes in repairing relationships being the be-all-and-end-all. It's not that you can't get anything out of working with those people, it's just that it's harder, because you have to pick through the bad guidance to find the good.
Either way, therapy will involve accepting your own role in things (your negative traits) and working on yourself, plus dealing with difficult emotions when they come up. For many people that, plus everyone involved being a little more understanding of each others differences, can go a long way towards repairing relationships and generally that would be the best outcome all round. For people suffering narcissistic abuse it's different. It's not usually possible to repair the relationship IMO, because there never was any possibility of a good relationship to begin with and the victim isn't the one who "broke" things. Relationships take two and it's very, very rare that the narc will ever acknowledge there's any problem from their end and work on improving themselves or the relationship.
You don't have to know though or to have all the answers. It's totally reasonable to go to therapy to work out if you want to try to repair the relationship or to let it go. It is helpful if you know (or at least have some idea) what you want from therapy before attending though, even if what you want changes over time as sessions progress and you figure new things out. Just gives the therapist somewhere to start from and a little insight into you. It's also ok to just show up saying you're feeling something but don't know what or where to go from here and just suspecting you need help. That will obviously take more time for the pair of you to pick through though before you start to get anywhere.