"If it wasn’t for our children then I would be long gone."
You're living with a man you can't bear to sleep with, who you suspect is still using prostitutes, whose friendship group reinforce such behaviour. You might think you're successfully hiding your repulsion from your children, but I doubt that that is possible.
Your children are growing up in a tense and dysfunctional atmosphere -this is really not good for them. We absorb what is the 'right' way to behave in relationships from the behaviour modelled by our family - what do you think your boys are absorbing from your behaviour? From his?
You need to stop thinking you are a judgemental bitch - you really, really aren't! His behaviour - and I'm not just talking about Amsterdam - towards you in particular and women in general is totally shit. He would "say how lucky I was that he wasn’t off whoring" - well that explains your low self-esteem!
You need to split. Your marriage is over and has been for some years. All that's needed now is to sort out the practicalities, and that is where you are stumbling. You speak of no family support and rubbish shifts, and you sound in a panic about it. Stop. Step back. What would it take to make it work? Don't immediately shut down any avenue as impossible.
For example, shifts - could change happen there? Could you move to a more 9-5ish routine working in a GP's surgery, or retrain as a health visitor or some other field in nursing that is less shift-based? Maybe that could be a long-term plan if retraining is involved, stay with him whilst you retrain then when your career is repositioned you can split.
Finances - look into what benefits you would qualify for, consider he would have to pay maintenance for the children, could this allow you to afford paid support? What hours would you need covered (under current shifts and future work patterns)?
You can't just wave a magic wand and it would all happen at once. But you can think it through and work out what steps would need to be taken to nudge you bit by bit to freedom from this man.