I really want to limit to the best of my ability the damage to the children when this goes down - and i dont know how to speak to them about her poor behaviour. i have never spoke bad about her to them (covered for her) and i dont plan to start - but when they question her behaviour i need an answer that isnt a lie and can somehow help them to start dealing with this change.
Hi Stylianos,
Wow. I wanted to get more information about your STBX and I think it helps if we share both sides and not paint the parent all one way. I understand how emotionally distressing and exhausting how all of this can be. It sounds like you've been on 24 hour duty and probably for sometime. Do you have friends and family members that are emotionally mature that you can talk to while you're going through all of this? Do you have time for you and take care of yourself?
I think you're doing the right thing. Kids are always watching their parents and they know. You don't talk bad about their mom and you're right, keep it that way

As I mentioned earlier your children have a bond with regardless if she's me talk ill or not, it's unconditional love. The kids need emotional support and guidance from a healthy parent and that's you. Someday, they'll need support with finding compassion for their mother.
Keep it age appropriate with the kids and try to keep them out of conflict as much as possible. I think what's key for kids is validation and validate how they feel. You're S5 may not be old enough to express, your D7 is old enough and if your kids feels angry or sad let them express their feelings and validate her. Validation is the anecdote to your ex spouses invalidations of the your kids. I'm sorry to hear about your D7 is being parentified in all of this, take comfort that she has you in her corner. Be their rock and be the best dad that you possibly can be.
Here's a thread that should help
How do I tell the children that their parents are getting divorced? Hang in there.
----Mutt