I don't think you're selfish - I think you're anxious, and cautious, and mindful of the potential effect reinstated visits might have on your household, and on your DD if SS's issues aren't addressed.
You may be worrying over nothing - but of course you don't have a crystal ball and the level of contradiction expressed, and the time all this has been going on, would make me err on the side of caution too.
IME, there is nowhere near enough consideration given in "the system" to the emotional needs of children caught up in their parents' battles when one (or both) of them have consistently used them as pawns. IMO, I wonder if this is due to a reluctance to "officially" recognise parental alienation because once the cat's out of the bag so to speak, then something would have to be done for the families affected - and of course that costs. Such as counselling for the children, and perhaps parenting classes for the parents who think it's more important to "get at" their ex through using their children, plus a real, effective deterrent for the ones who mess with contact, denounce the other parent and so on - even if that does ultimately mean either a literal punishment of some sort, or being punished by residency being changed.
And of course there seems to be practically NO thought at all given to the effect contact problems can have on other children in the family. It has felt to me - both personally, and when hearing about other people's stories, that only the "disputed" children seem to matter so far as the courts are concerned. Decisions are made - which in theory are in the best interests of said child(ren) - but those decisions aren't always necessarily the best one(s) for the family as a whole .... and that strikes me as so unfair and wrong. Except in life and death emergencies, in every other situation, most decent families consider all the kids before making decisions, and think about how everyone will be affected. If you're a "non-disputed" child for want of a better description, and your siblings are caught up in a contact case, you will often just have to get on with and fit round with whatever the court decides (if that makes sense). IME, DP's apparent (I wasn't there) attempts to explain how various scenarios would impact upon our youngest were more or less brushed aside - yet this is a family issue, and though obviously the "absent" child will be the main focus of any hearing they don't exist in isolation.
Anyway (sorry for rant there) ...... re: counselling, am not quite sure how it works with children. Obviously as adults we can refer ourselves to any number of counsellors if we have emotional problems and don't have to go through a middle man. I can see how court ordered counselling would be preferable to avoid any arguments from the ex, but when DS is with DH surely he is just as entitled to arrange counselling for him as his mother is (or isn't) ? Assuming this can be done for children without referral being required from school, court or a GP, would this be something for DH to consider ? I expect he might be reluctant in case DS takes offence but I think it would be really sensible to try and iron out any lingering confusion/anger DS has before full and "normal" contact is resumed at your home. Not least because in your shoes I'd be concerned about my child re-establishing a relationship only to have it whipped away again in a few months if DS decides to vote with his feet again for some reason. Perhaps it could be sold to DS as his dad wanting to "sort out" their relationship so he isn't made to feel "at fault" .... I dunno, but a child experienced counsellor could perhaps suggest the best way to approach it so he's not like a rabbit caught in the headlights. And if possible, I think it should be something DH and DS do together.
Just thinking out loud - I actually don't know if what I've suggested can actually be arranged without official say so. But if it can, then surely it wouldn't need the mother's permission as DH is equally entitled to do what he thinks is best for DS.
And of course no way should DS get "special treatment" - very very unfair on your child, but also won't resolve any of the issues which have led to him being so unrealistically demanding.