I too am sorry. I do not know much about the laws in Greece, but, whilst I can see them wanting you to support your children, I cannot see that they expect you to pay more than you an afford otherwise there would be a ton of ex husbands jail. They can't expect you to pay more than you have ... the maths simply don't work. It cannot be in the state's interest that a man who cannot afford to pay what his wife demands is in jail, because quite simple, he is not only still not paying his wife the support she demands, but the state is also paying to house him in prison.
You mention meeting with her lawyers, but have you seen your own lawyers to confirm. If not, then do so immediately.
My second suggestion is to stop worrying about whether she is having sex with others and whether it is sick or not. If she is having an affair, she will continue to have an affair, emotional or otherwise. the types, positions etc shouldn't matter. You are only torturing yourself.
The terror ends when you stop seeing it as terror. Get up and find out what you can and can't control. You can only see your son for 4 days a week, them make those four days the best four days possible. Use every other day the to work on you.
Sort out your finances, look for a job, start running, go swimming in the local public pool, join a walking club, do anything but sit at home and ponder "what positions she might be having sex in".
