Oh Lost - I'm so sorry to hear about all of this.
TBH, I'm reluctant to post much, as you WH has been on SI, knows you've been here, and may be reading this thread. Unfortunately, I cannot PM you bc you don't yet have 50 posts.
Am I wrong about his sinister behavior
TBH, who knows. Sounds like you have good evidence of some sneaky stuff that IMHO goes beyond "typical" (whatever that is ) wayward thinking/behavior.
I could be off base here, and if so, I apologize... but I did spent a LOT of years in the divorce world.
First and foremost - I think it would be wise to see an attorney IMMEDIATELY. If he is downloading software and using your login on other devices to track you, it is STALKING, so the question for a local attorney is what are the laws in your area about spousal stalking / data privacy. You could also contact the local police, but they tend to not want to get involved (esp if he called them on you before... which did not bode well at the time and looks even worse in light of your post today).
I know it's a big step, but if possible, you may want to consider getting an order of protection - first & foremost bc the tech crap you describe IS escalation / controlling behavior that is NOT healthy/normal, and second bc it shows you mean business and WILL protect yourself and your children. Some states will also make allowances for the financials (maintenance / child support) and custody agreements as part of an order of protection (IOW, depending on the laws in your area, it MAY be a way to get some preliminary financial/custody parameters set w/o having to file for D.... so you don't have to file for D, but you ARE taking solid steps to protect yourself right now. Again, this varies a lot from state to state, so what works in my state may be VERY different from yours).
I'm not tech savvy enough about the logins/passwords... it may not matter but I would probably try to use another computer (e.g. at my local library) to access my Apple account and change the passwords, etc. I'd probably get a new gmail account as well and use that as the login. I may consider changing banking or other passwords, but may want to talk to an attorney before doing that (again, each state is different). IMO the updating the other phone with YOUR apple ID is a big big no-no, esp after you asked him to return the device he used to download YOUR data (IOW, any "consent" you may have given prior was rescinded when you confronted and asked him to return the other device). You may want to contact Apple about it as well (tho I have no clue what, if anything, they would/could do on their end). It would be a lot of time/work/energy, but if it were me, I'd probably backup the phone, then factory reset and start completely from scratch (ie would NOT restore from backup that may have spyware on it). I believe there are programs that can help to backup/reinstall only specific components (e.g., your contacts - I have my iphone set up to use contacts & calendar set up in Google, bc it's a lot easier to xfer data from one google ac to another than it is to do via IOS).
If you don't already have one, may want to consider opening a credit card in your name alone - it is, unfortunately, VERY common for estranged spouses to cut off access to credit / debit cards (in my area, this is met with STRONG consequences by a judge, but the kind of person who will cut off credit/debit to a spouse and their own kids isn't thinking much about consequences or believes they'll be able to talk their way out of it, a tactic I never once saw work during the years I was in the divorce biz).
The other thing is to document, document, document. Whether there may still be a path to R or not, right now you must protect yourself and your kids as if you will D. Only communicate with him in writing, and then screenshot/print/save EVERYTHING - ideally with a copy saved with a friend/relative you trust.
All of this includes the 180. No more talking about the infidelity or the M. Limit it to kids and finances for awhile. You can ALWAYS re-evaluate where you are / what you want / what you see in him changing (or not). IMO, the stalking is like throwing down a gauntlet that kind of shifts all the perspective.
just my $0.02.
Sending mojo to you. Dealing with trauma and trying to heal from infidelity, in and of itself, is already hard as F. Adding a WS who is engaging in some very sketchy / harmful behaviors adds a whole other level to "hard".