It makes perfect sense Wet do you realise how big it is though? I get the feeling it really doesn't feel like much to you, or maybe, worse, it has thrown your perceived shortcomings into sharp relief, I hope not. You might feel a bit of a tit but, stick with me, can you focus on 'now I know where I am' and then can you just roll it around in your head for a minute, just that 'now I know where I am', not any of the other things you moderated it with, just that - does that feel powerful? Does it feel grounding? Can you keep thinking it until it does feel that way (I pretend to be Brian Blessed but you know, whatever works for you 
) You know where you are, that's powerful insight to have. It doesn't matter if you are at the very bottom or the very top, if you don't know where you are and I mean both: where you are and where you are, then you can't move anywhere else.
Self worth and self esteem are muscles that grow with use and can atrophy when they are suppressed, it might feel like the opposite but it's hard to destroy them completely even after many years of onslaught and a tiny speck is all you need - but you are already worth knowing, and I would bet you real money that you could do what you want to do tomorrow if you went headfirst through the fear of it. I'm not suggesting you do do that but that it's all there in you still - you are competent, you are capable, you are likable (I like you already) and you are able, you don't have to add anything to yourself, you are already and always have been perfectly, amply, sufficient in every respect, you have to remove what has been added to you by criticism and control. You may have been told so often you believe it, with a unhealthy dollop of all the things that go along with that, but you know where you are now. Right now, today you absolutely can stop believing it. You don't have to move a muscle, nobody will know, but you will have started a revolution. Make it a conscious choice to contradict! I challenge you to a kind-off, I can think of a number of nice things I'd say to you, I would be delighted if you said more about yourself (I don't mean you have to do it here out in the open) and meant them. If you haven't guessed I'm unashamedly lentily.
As to being a bit of a moaner during your last year with them, well, shit, that's life! Work can be hugely stressful and have a very negative impact on ones mental health when it goes bad, many people have dealt with that...by moaning their arses off to their mates, repeatedly. I spent a run of God knows how many years being that person after job shite and then my mother getting cancer (twice, two different ones right after the other because apparently my mother goes all in), my grandfather died and my dog and 2 of my cats died all in a row. My friends listened to all of it even snotty, crying calls at odd hours. Because I wasn't only that to them, and neither were you. If you feel that you want to put this away now and move on, that's fine, make your peace with it. That's perfectly ok to forgive yourself for. Honestly, and I expect they would too. But can I just draw your attention to one thing: you said that it was you at your worst, you were selfish and self centred and they won't want to know someone like that.
Examine that sentence, it's not a sensible sentence and does it align with everything else you've said or does it look sort of mashed in at the end to revise things a bit?
You might have been at your worst, that's understandable. The actions you chose to protect yourself may have felt selfish and self centred - to you. Are they possibly being magnified by various baggage that you don't need to hang on to? But mainly I'm wondering what happens if you say no even if you disagree/don't want to do something? Most people don't demand obedience. You went against your conditioning to uphold it, cognitive dissonance agogo! It will feel worse to you. We can behave badly, we are fallible humans, but is what you did irrevocably terrible? No. We are also allowed to fail to be perfect acquiescence machines under stress. 'A bit shitty' is not the epitome of condemnation! They won't want to know someone like that - well now you're just speaking for them based on what you see, they probably didn't see the same you and 'like that'? You're not like that. It's easier to reject before you are rejected but to be quite frank - nobody is just nice enough to support a friend, speak to them, socialise with them for so long and so successfully be nice that they betrayed no hint they didn't want to know you anymore and would just be quietly relieved you left. Unless you're going to tell me your friends were the Dalai Llama and some top knob monks. I know lots and lots of nice people and I still couldn't round up a group that could keep that up. They probably just actually liked you. It happens.
I'll leave you alone now before you set your laptop alight just to stop me typing at you but - keep going 