Ah zig, take a few breaths here. You don't need a 2x4 for EVERY aspect!
Your friend is wise and spot-on with her assessment of the situation (does she know about DB??). I concur with what she suggested.
I think part of "rectifying" the situation about having H not tell you about his OW plans is to act as if you don't care about what he's doing. You admit yourself that you are not really detached in respect to that. That is a good place to focus to start.
Originally Posted By: zig
Add s into the mix: if i shrug and say - it's your turn this week, you'll have to keep him, i run the risk of him getting pissed and just bringing ow into s's life when it may not happen if i just let him decide about how things are.
This is kind of exactly what you need to say - it's not your place to fix his scheduling issues especially when he is trying to change a schedule that you already had in place. You can try to set boundaries wherein you say that it is not acceptable for H to introduce S to OW right now b/c it will be harmful to him. However, you cannot control what H does or be concerned with his reactions - this is at the heart of detaching.