I think that you need to start to take some ownership over your life, OP. You can’t blame everyone else but yourself, but you do need to accept that you carry some of the responsibility for the situation you find yourself in. These things weren’t just done to you, you weren’t a passive passenger with no agency or choices. You had choices, you made some that you clearly now regret. And you were also strung along- but, realistically, you must have realised that was the case and still chose to stay. Once you accept you were the co-author of your own dissatisfaction, then you can make changes to put yourself in a different position.
You cannot avoid the facts made a series of choices to stay with this man- he may have strung you along, but you could have decided after a few years that your desire for children was more important than your relationship or the lifestyle it provided. But, for whatever reason, you decided to stay with him. I think you must of known by the time you were heading towards 40, and definitely by the time you were in your early forties, that you were heading into “now or never” territory, and still made a choice to prioritise your relationship.
You should have been saving and paying into a pension, given you were not married to your partner. You also seem to have known for a long time that the house he owns and his pension are going to his children. Which is right, I think. Having not saved, I think you should try to do so now- could you perhaps look into buying your own property?
It is also clear that your relationship is over. You feel too much anger and resentment towards him for this to work. And i’m not saying you are wrong to be angry, but really why continue a relationship with someone you don’t like, who you resent, who you feel has lied to and betrayed you?