This is only a short reply for now, but just to say I understand a lot of those thoughts and feelings, especially around the effects of long-term isolation. I have some friends who I don't see very often but contact by email and sometimes phone or skype, but many times, I pause and don't make the call due to being too fragile in case the response is not empathetic.
If I have been isolated for too long, I try to go swimming, at least - this 'shifts the energy' a bit. With you, regular activity MIGHT help a little with the insomnia. I realise you must have tried all these things, so sorry for stating the obvious.
Isolation is bad: we end up acting like those poor zoo animals you see rocking and gnawing at themselves due to their distress at not being able to live normally.
I'm not an expert, but would advise you to try to build your self-esteem a little by taking those steps to reduce isolation - even phoning the Samaritans insteaad of a friend just to talk all the problems out: I have phoned so many times when so distressed with sheer loneliness (I am alone 99% of the time) and ALWAYS now when I am on the brink of self-harming - this happens occasionally when I become suddenly very very distressed or angry and is mostly to do with a dysfunctional friendship I have with a man where I have had to battle obsessive feelings. I have known him for nearly four years and at last the feelings are settling a little and the friendship is still there.
If you and I were to build ourselves up a little wih swimming, joining a walking group (in nature), contacting other humans via this forum, or the Samaritans etc., then we are a bit stronger to deal with those 'blows' from friends and family. I have always been overly sensitive and will ruminate unhealthily for days and weeks about a tiny slight from someone, or from them not understanding me.
Even one of my closest friends has shocked me and hurt me badly with her lack of empathy, yet is in other ways the best friend a person could have. This last Christmas I had NO invitation from four different households of my immediate family, including both sets of parents and two sisters etc. THis friend invited me (as she did last Christmas, which I spent with her and her two grown up sons): she knew I had no other invitations and said I would be always welcome in her home - always and at any time. I even lived there for three months between house moves a couple of years ago, and she was/is the most generous hearted person.
YET, she does not share my beliefs and feelings about animals and when I was absolutely devastated when my dog died, she told me to give her dog a cuddle and was very dismissive, because she personally is very strong emotionally and is very 'oh well they had a good innings' about bereavement: even when her own mother died she was very practical and stable about it. She expressed some sadness - she's not a robot! - but so psychologically stable to the point where it shocks and baffles me, as I am the diametric opposite.
Anyway, it hurt me SO much when she couldn't empathise about my dog's death - I thought she might at least pretend to care and comfort me through it but she could not empathise on this issue - full stop. I wanted to scream, if a woman lost a child would you say, here hold this one (another child) and expect the woman to be comforted?
It took me a while to get over that. But over the years I have accepted that we all feel and perceive things so differently. I am a aware some of this may sound patronising and I don't mean it to.
And I've rambled on...! Just to say, I think tackling the existential loneliness is so important here.
With best wishes.