AIBU to explain to DS (8) about his dad's mood problems?

[RampantPumpkins]

DS's dad (we're separated) experiences mood fluctuations that resemble bipolar disorder. He has been 'unofficially' diagnosed with this by a couple of professionals. Who knows if he has or hasn't, but the reality for him is that he is depressed for months at a time (about a year last year and into this year, for example), stable for shorter periods (maybe a few months), and then manic for up to six months at a time.

Over the years, I've come to realise I can handle the lows (easier now we're not together) and the in-the-middle stable phases, but not his highs; I just can't. When he's elevated in mood, on top of all the other things he does which don't really affect me now (minimal sleeping, lots of new projects, lots of spending and investing that amount to little other than debt and another depressed episode, etc), he stops treating me respectfully. We co-parent really well most of the time - take DS out for dinners together, day trips and even a weekend away, pop into each other's homes during pick-ups/drop-offs, etc. But when he's manic, it's as though his perception of me changes. He becomes cutting and contemptuous. He says things which really hurt, and attacks my character. He dredges up things from our past (we've been separated a long time!) and says things like, "Well, you're the only person I have this problem with," and when I challenge his new attitude, he says, "Well, I?m just standing up to you now." WTF?!

I end up feeling miserable, violated and start doubting myself. And then when he comes back down, he'll be apologetic and it'll be fine again for months and months. It's emotionally and mentally exhausting.

He seems to be heading for a high at the moment, and inevitably, we ended up clashing tonight for the first time in ages. I'd said something that I thought was innocuous, thoughtful and helpful even, and got a cutting earful from him. I was floored.

So, what I want to ask is this:
(1) Is it OK, when DS's dad is in this elevated mood, for me to move to more parallel than together parenting? I'd have to spell it out to him - no popping in and doing parenting stuff together for a while - which might piss him off, but I feel I need a boundary in place for a while, while he's like this and likely to lay into me after the slightest real (or imagined) provocation.
(2) And is it therefore OK, now DS's 8 and fairly mature, to explain why things have to be different for a while (i.e. less contact between his dad and me)? I don't want to do the your-dad's-a-shit thing, and I want to encourage and support their relationship - but I feel I would need to explain why the dynamic has to change for a while. Can I say something like, "Dad goes through these changes in mood, and that's how Dad is and he can't help that, and mostly, it's fine. But when he gets into a certain kind of mood, I feel he doesn't treat me well enough, and so I need a bit of space between us for a while." What do you think?

He had affairs, blew obscene amounts of shared money and took drugs when he was on a high while we were together, and I have no intention of telling DS about all this unless he beats it out of me when he's much older. But is he old enough now to at least understand a little bit about how his dad is, and the impact this can have on us all sometimes? Is it fair of me to say/do anything at all? I don't want to be laid into by his dad, and not set the example of making a stand; of saying a line's been crossed and I won't put up with that.

Hmm. It's difficult. Sorry this is long. Grateful for any thoughts though. Thanks.

[Jux]

I think you sound like you knoww what you're doing. What you have proposed sounds pretty sensible; setting boundaries isn't just to make you more comfortable, but also serves to illustrate to your ds that there are lines which one does not cross and shows him thAt respect is important.

How does your ex behave towards ds when he is manic?