@helplesshopeless
Unfortunately he said he was about to submit the divorce filing but now won't tell me whether he did actually do it or not, so everything is a bit up in the air at the moment.
I'm so sorry. This is step 1 of the mental torture he apparently likes to inflict on you.
If the tables were turned, would you treat him like this? Would you withhold information deliberately, to intensify his pain and control him with power games?
I'm afraid his approach will probably be to use the thumbscrews on you emotionally, e.g. by rubbing your nose constantly in how upset he is. He knows how much that distresses you.
Just remember that the reason this is all going to be a bloody, horrible mess, instead of a civilised arrangement between adults, is that he is not interested in doing things nicely. All the time you are agonising over making things easier for him, he will be making sure things are as difficult as they possibly can be for you. It's because he really doesn't care about your feelings at all, or at least only in relation to controlling you in relation to him.
And that's precisely why you're in this situation in the first place. It really is a proper tragedy, but of course the tragic hero is blithely unaware of the faults that compel him to his fate.
Sorry, this really is going to be horrible. Massive, massive respect to you for getting this far. Sending you all the courage and energy you're going to need to get through what's ahead. 
Please try to keep in mind, for the sake of your own sanity, that he is stormy and thrives on chaos. There's a wonderful bit in Chanel Miller's Know My Name that might help:
I used to shrink at harsh tones, used to be afraid. Until I learned it takes nothing to be hostile. Nothing. It is easy to be the one yelling, chucking words that burn like coals, neon red, meant to harm. I have learned I am water. The coals sizzle, extinguishing when they reach me. I see now, those fiery coals are just black stones, sinking to the bottom.
Good luck OP, try to find some space to treat yourself with love, patience and kindness, because he certainly won't. 💗 One day you will look back on this and I promise you will think it's the best thing you ever did.