Thank you for your messages. To answer a few of your points...
DS is 11 now and able to say what he wants.
The reason why I say it is a 'good deal' for Dad is that he does not have Parental Responsibility (DS's birth pre-2003 law change); but I have provided him with opportunities he would have had had he had it. In the main, he has refused to partake in decisions which affect DS - saying I have a handle on it. And refused opportunities to contribute in areas marked as legal responsibilities. He seems to contribute only when he wants/can see an opportunity to make himself look good. I will of course be savvy about any mention of this point to CAFCASS.
Yes I agree it is about a good deal for DS (entirely).
The fortnightly contact has been an informal arrangement for over three years and DS is settled in it - if not always happy. It was more frequent but DS was coming home each time complaining about aspects of his care - lack of supervision, Dad 'bad mouthing'/undermining me, non- administration of essential medication, junk food (son is on a medically controlled diet because of a blood disorder) video nasties - leading to nightmares/bed wetting, being left with people he didn't know very well (safety issue), Dad not spending time with him, wearing clothes in bed that had been worn during the day etc etc. He was also withdrawn, emotionally erratic/not his usual chatty self. He returned unwashed and smelly - the house is disgusting and aggravates my DS's allergies. There are a number of other examples. He told that he was feeling unsettled because he was 'a guest' at both houses and I noticed that his going away bag was increasingly unpacked when with us. This combination of things help me make the decision to decrease contact.
I have raised DS's points with ex (in a variety of ways) - but he has not provided any real answers to the issues raised. Or his answers show that he is not really thinking about the consequences of things for DS.
It has been very difficult to support contact under these circumstances and I have had moments when I have thought of stopping contact. I find it difficult to weigh up the pros and cons for DS. Is it better to have contact that is a challenge , rather than non at all? I think I was waiting for that definite moment when ex went just to far. I find it difficult to weigh up whether the above is just standard in separation cases or whether I need to take more affirmative action. Ex knows this and has been holding the threat of court over me to try to ensure contact.
My parents had a less than amicable divorce when I was 11 and I lost contact with my Dad at 15. I vowed that if my relationship would ever split I would do all I could to ensure contact between DS and ex. Ex knows this and has said, ' Do you want things to turn out as they did for you and your Dad?' when I have raised what DS's complaint. I said that because of the past I am actually stronger and have a better understanding of how to conduct things for DS.