I can understand your concern at not hurting him, but keep in mind that he is good at deceiving. The fact is while you may see the honest side of him (He has no need to lie, as you accept that he is married) he is being sneaky and deceitful to his wife. So if he is able to pull the wool over her eyes so well, you have to accept that he could be manipulating you as well. The fact is you feel guilty for cutting it off......when you should feel no guilt. He is the person who makes these choices, yet you feel bad for him. Have you asked yourself why? Men who cheat tend to be very manipulative and often have their wives and mistresses eating out of their hand and feeling bad for them. When in reality they are the one being dishonest and unfair to both women. But these men know how to suck women in and make them believe just about anything they are trying to sell. He tells you you are part of his "Inner circle" but the fact is if you were then he would want to be with you. But by telling you this, and pulling you in you trust him even more and are willing to stay with him even though you know it is not healthy for you.
I know right now that the last thing you want to think is he has conned you........but the fact remains that he is willing to allow you to waste your life giving up a future to satisfy his own needs. Now you have to ask, if he really loved you, really cared for you why would he want you to live like this?
When a man really loves a women there is nothing he will not give up for him. Just like when a women loves a man there is nothing she will not give up for him. We see this everyday when men walk away from jobs, family, wives, children etc to be with the women they love. While it may not be easy, the reality is if he really loved you as much as he tells you he would leave his wife and kids. You may not want to hear that.........but that is the truth. If he was as concerned for his kids as he claims, then he would have very high ethics and morals.......which does not mesh well with the type of man who cheats.
I know you want to believe what he is telling you, but the fact is he is lying to his wife and children and he is likely lying to you. Cheaters seldom really love anyone, they feel entitled to seek out their own satisfaction regardless of who it hurts. In this case, he knows it will traumatised his children if he gets caught..........yet he has continued this for a year. Does that sound like a man who cares so much for his kids he would never leave them? So then you have to ask yourself if he cares more for what he wants then what his children needs..........why does he not leave them to come to you if he loves you so much? The fact is cheating men seldom love any women, they do not know how to love. Love does not lie, love does not cheat, love does not hurt intentionally. He is making the choice to lie, cheat and hurt not only his wife and children but you as well.
Knowing all that you must sit down and make the best choice for you and your future. As for his feelings, if he really loves you as much as he says that this hurts him then he will give them up for you. Which would be a sad outcome in the end as his kids deserve their father.
As for advice on how to move on, the first step is to end all contact. If you allow yourself to stay in contact with him then his hold over you will never break. He will continue to manipulate you and make you feel guilty over leaving him. Moving on is not always easy, but getting out and meeting new people will help. Don't allow yourself to wonder "What if" accept that you have no future with him and make the firm choice to move on. You may want to consider therapy to talk about your feelings with a neutral third party who can help you stay firm in your choice and better understand why you allowed yourself to fall into this position in the first place. Sometimes we tend to gravitate towards relationships that have no future, a therapist can help you understand why you did this and prevent it from happening again in the future.
One day at a time...........I know that sounds silly. But don't look at this as forever. Look at it as "I will not contact him today" and everyday tell yourself that and you will move on.