To say no to ex coming round to see his DS?

Yes you can say no and in your place I'd get a restraining order.

Also I’d check the home for trackers or get someone in to do it, and DS bags.

Hard no, you are being perfectly reasonable and how you feel makes utter sense. Tell him, ‘that’s not possible. XX is fine, much better now, nothing to worry about. They’ll see you on Tuesday as per our arrangements. Bye’.

Please get a ring door bell.

Explain to DS that his Dad isn't coming into your home again and he can pick him up at end of path.

You need to say something to DS. What if ex asks for his house key at some point and let's himself in.

Take back control.

As for tonight, tell ex he can Facebook DS.

Exactly. If op is inferring that ex is great then that could undermine any red flags that Ds could be feeling. At 12 he is old enough. He is also at that tricky age where he might start having challenging behaviour and pushing boundaries as teenagers do, which exh may not respond well to if he's abusive.

You can tell him in a very matter of fact way. Tell him it doesn't mean anything about his relationship with his dad needs to change but it is reasonable to tell him that you are afraid of his father. The tracking incident I think is really important to tell him as it's pretty concrete and impossible to explain away by saying things were misunderstood. There's really no circumstances in which that is acceptable. Your ex seems to be ramping up his behaviour again so even more reason to warn ds so he can protect himself and warn you about worrying behaviour.

He’s invading your space. You do not have to let him in your house. Ever.

If you don't have an appropriate conversation about his father's abnormal behaviours then how do you expect yo protect your child from being either used as a tool to get to you or being treated the same way eventually?

This man uses the excuse of love to control people in his life, he loved you right? Look at how he treated/treats you.

He loves your son right? He isn't safe from this treatment op.

No way should you allow him into your house. Your son is old enough to FaceTime his dad whenever he wants to.

I would tell your son why you split up because sooner or later your ex will be telling him all sorts of rubbish about how you dumped him for no reason.

He put a tracker on your car?
He would never set foot in my home again.

At 12, your DS can give his Dad a call to let him know that he’s starting feel better, there’s no need for his Dad to come around.

I agree with the suggestion to get a Ring doorbell and change your WiFi password. I’d change it every few months so there’s no chance that he can use any devices in your house.

Also, given your DS’s age, I can’t see any reason why your ex ever needs to be in your house.

You NEED to be honest with your son about why you separated, because if he was that controlling with you, he might well try and start with your son. He's old enough to be told. This is about safety for BOTH of you.

Get a Ring doorbell and check your home very carefully. Coming in regularly would make me worry that he is swapping over devices to check the footage.

Maybe change your Wi-Fi password. Make sure DS knows not to give it to his Dad.

Jesus, he sounds dangerous and a like he can't let go of you. Be very very wary of him weaseling back in. Don't let him in your house. Do you have a ring doorbell?

Have you been honest with ds about his father? He needs to know that he hasn't treated you well and you don't want him in the house and why.

Doesn't mean bad mouthing him but I'm always shocked on here that some mothers dont tell their children an age appropriate truth about their other parent.

If he treated you like that then there is a chance he will do it to his child or another partner and ds needs to know that you found this behaviour inappropriate and it's ok for him to feel that too and not normalise it rather then being told his dad is a stand up guy.

If ds knows then great, ignore the above.

Might be worth telling ds about the recent issues, seeing him drive passed the house and that you think it's 'strange'. Might be a prompt for ds to tell you about more odd behaviour.

Were the police involved when you found the tracker on your car?

I'd not be letting him in ever again and checking for devices in my home and on my car. I'd also check DS phone.

Fwiw my ex is very similar and the above wording is what I used, he HATES it but I don’t care.

“Ex as DS gets older and has adjusted to our separation, I have been thinking about boundaries. From now onwards, I will drop him at yours but not come in and I will appreciate the same in return, there is no need for us to go into each other’s houses”

Yanbu. I wouldn't say anything about your personal feelings on the matter though just that you think it will be better for your son if there are clear boundaries between parents so it doesn't blur the lines or give him any false hopes that you'll get back together

He's using this as a way back in. The longer you allow it the more difficult it will be and more push back he will give. Given his history and stalkerish behaviour (driving by the home) I would be genuinely worried. Its time to draw boundaries

Absolutely I wouldn’t let him in my home. At 12, your DS is old enough to go out of the house without you needing to be there and meet his dad in the car/at the bottom of the path.
I would also check very carefully for hidden cameras anywhere in your house where he was able to go when he was there.
As for tonight, DS can FaceTime him if well enough.

Sounds like an excuse to get in your house Op, give him an update on the phone but tell him no to visiting. He can't be trusted so if he's banned from your house it's his own fault

Fair enough, but still, no he doesn't need to enter your house, your son is 12 they can talk over the phone just fine.

I would be making some time to talk to the police btw, he is essentially stalking you and this behaviour doesn't fade away it nearly always ramps up.
They quite often create scenarios to make opportunities for themselves.. which is why I asked about your son.
Get some advice on what procedures you have available if he escalates.

Tell him no he's not welcome into your home, he'll need to wait till it's his turn with ds then ignore the door.