This is a typical behavior from a high conflict bio parent and grey roack (not reacting to their bad behavior) is the best course of action when dealing with one.  But you can't grey rock everything, no matter what.

When you're dealing with someone like this, you have to learn to pick your battles.  What are your hills to die on and what aren't and act accordingly.

The cell phone was banned very quickly from our house.  SD and DD both had their phones taken (they were being jerks in a store, as I recall) and SD informed me that BM said we couldn't take the phone away because it was her property.  We took it back to BM that minute and it hasn't been back.  We did the same when SD tried to bring a tablet and when she had both kids in Fit Bits.  A hill for us to die on is privacy.  I can't prevent the skids from telling her our life stories, but I can keep her from tracking our movements.

You and DH need to talk about what your hills to die on are.  Those are your boundaries and your DH needs to enforce them.  You both need to get out of the habit of trying to hold BM accountable for every.little.thing because all that leads to is hate and discontent for you--not her.

Family courts are unreliable.  If you take legal action and nothing is done, she will be emboldened and you will be frustrated.

BM will do as she pleases if she knows Dad may get annoyed but there will be no real penalties for being and doing what she does and is. She has nothing to fear. 

IMO, you keeping a journal will not be helpful to your own health and well being. Why? Because DH isn't going to go back to court and do anything about it. So what I imagine happening while you record your journal is you becoming more and more frustrated and having BM in your head even more than you currently do. Look back over all your blogs. You've pretty much 'journaled' here for quite some time.... nothing has changed for you and DH seems to just get worse with his lack of parenting and lack of doing anything about BM.

You have the kids coming up here (June?) for the one month summer exchange. Between the food bit, the sleeping in livingroom bit and , of course, BM trying to come over if the kids sneeze or want chicken nuggets while Dad and you are working, I'd be tempted to take a week off work (if you have the PTO coming) and going on a vacation to go see/do something you'd enjoy by yourself. Whether that is with a female friend vacation or a trip to visit family or just relaxation at a hotel with nice dinners and sight seeing clear across the state soaking up sun and having peace and quiet. 

I think that a journal may in fact be a good thing to start keeping .  You should track when she doesn't follow the CO.. noting when it was with permission and without permission.  If your DH allows a variance, that is not really wrong, but you still want to track it because you can point out to her all the times that he was accomodating vs her accomodations. 

The hills to die on concept is also important.  When you vent here (and I understand it's venting).. you seem to be just as enraged about the important things as you are about the minor issues.  Your own sanity will require you to figure out how to get past the minor issues without them tying you in a knot.  Figure out the big issues and let them be the focus for fights when necessary.  I'm not saying ignore the small things.. certainly note them in your journal, but no need to have WWIII over every minor disagreement or lapse.