He is branching out. You have thwarted a healthy desire to extend his social circle and take steps away from home by placing unreasonable barriers in the face of his desire to maintain a relationship with friends. You have driven him into something that is far less safe.
I agree with MoreCrackThanHarlem wrt your rules. My DCs do not go out and wander around in the evenings. None of their friends do either. I have them involved in sports that have evening events (basketball, volleyball, badminton, swimming), and they also have a lot of homework to do. They are also expected to contribute to preparing dinner and clearing everything up. All of this eats up the evening nicely. Like MoreCrack, mine sometimes go to a film or out to eat, and since this is a concrete destination and solid plan it is ok with me. But there is no hanging around, wandering the streets, drifting into people's houses and out again, winding up in the darkest corner of the local parks or behind the railway yard, etc., with a few bottles of cider and cigarettes or whatever else anyone wants to try.
They do go on sleepovers and out on weekends as long as there is a plan with a destination and solid times involved, with the proviso that if their grades in school slip or if they find themselves having to stay up past midnight to finish work we will sit down and think about their time management together.
They provide me with contact numbers. I have at this point dozens of numbers in my phone, stretching back to the mid 2000s from DD1's teen years. I probably called about five of those numbers in the course of their teens. One rule I have that is not negotiable is that if I call or text when they are out then they have to either pick up the phone immediately or call or text me within fifteen minutes. The consequence for not calling back or making me wait is to have me take their phone for one day afterwards. It may not seem like much but it is realistic that one day is a painful one and there is scope for escalation of my consequences if there are signs of unreasonableness. The other rule is that if plans change they must call me and inform me.
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Your choice of how you expressed yourself conveyed very well the feelings you had (tear stained/white faced/ little mum), and you confirm that you felt small and powerless.
You do not understand what boundaries are if you use the phrase 'He pushed his boundaries way too far'. A boundary is not a rule. A boundary is not a leash on a dog that gets overextended.
A boundary is a healthy sense of self respect and a healthy sense of respect for other people. Your son defies you, and argues with teachers in school. He appears unmotivated in school. Your son does not have healthy boundaries.
He and his father have fallen out and this is the major elephant in the room that you are spectacularly ignoring right now. You have described your exH as an authoritarian parent, which is a style that can backfire horribly especially in the case of boys when they turn into teens. Your son's experience of authority and respect has been very negative and not conducive to the development of healthy self respect up to now, (and if your exH was in any way abusive towards you then his experience of that needs to be addressed too because that will have had a big impact on DS even if you think he was not aware of what was going on.)
"I think the trust foundations are put in place earlier on when a child understands that you would rather deal with the truth no matter how bad it is than him putting his life in danger "
Your son is not going to share the truth with you when he sees you all white face, tear stained and upset on the couch.
If you think that sort of demeanour and attitude on your part doesn't do harm you are terribly mistaken. It harms you because it makes you look weak and afraid and it harms the relationship with your son because you are asking him to be responsible for your feelings. It doesn't help him develop a sense of personal responsibility for his own behaviour -- it doesn't contribute at all to the development of healthy boundaries in other words. It will just make him hide important facts from you to avoid the unpleasantness and the manipulation.
Above all, it doesn't give him the confidence he needs that he has a solid and dependable parent. Making a child responsible for your feelings turns him into the parent but you are trying to make him follow rules as if he were a child. You are not encouraging the development of healthy boundaries here. You are creating difficulties for him as he tries to figure out how to make good decisions when you throw the complication of 'minding mum' into the equation.
It is extremely important that you behave in a way that lets your son know that you can handle anything that comes your way.
Sitting up white faced and tear stained and indulging your inner 'little mum' is not the way to portray a mother who is on top of things, in whom her son can have confidence. He needs an authority figure, not someone whose anxiety has got the better of her. By authority figure I mean someone who is able and willing to lead, not resort to reaction that is manipulative.
By lead I mean sitting him down, explaining your valid concerns in a way that does not overegg things, and asking him to come up with some way you can both achieve what you want in this situation. He may want complete freedom. You are going to have to explain to him that a compromise is what you are asking him for, because that is not an option. He may surprise you by being reasonable, showing signs of understanding your concerns.
Your discussion needs to range over his relationship with his dad. This is a bull you are going to have to take by the horns. Listen very closely. Ask him how he feels about your relationship with his dad. Do not cry. Thank him for any sharing of his real feelings he offers.
The subject of school needs to be addressed too. Again, listen. Ask him for suggestions about improving the situation there, what he can do instead of arguing with teachers. 14 year old boys are not the best at looking ahead even to the next week so do not be tempted to dive into 'what-are-you-going-to-do-with-the-rest-of-your-life-if-you-fail-in-school?' territory. Ask him what his goals in school could be in the very short term - week by week - and what he is going to do daily to achieve those short term goals. You need to establish the fact that he is accountable to you for his conduct in school and you need to work with him to find a way to improve things. Going forward taking baby steps is often a fruitful approach as long as things don't sink to the level of one person nagging and one person resenting. You need to ask him how he is going to solve problems.
Wrt trust:
It is always a case of 'trust but if there is any niggle of doubt, verify'.
And there is always a Plan B, which is 'Call me and I will extract you from the situation on a No Questions Asked basis, and if any of your friends want to get out too, they can pile into my car and stay with us overnight.'
You have to keep on encouraging the good decisions and the only way to do that is to allow them a bit of leeway so they can understand consequences for themselves. It is a fine line to tread. When a good decision is made you need to show approval. A poor decision is trickier to handle. 'I told you so' has limited effect. Asking them how they could have made a better decision can help them come up with their own judgement of a situation next time. Teens really do need feedback and they welcome it despite what you may think, but they also need to have a feeling of autonomy, and to have their need to branch out honoured and facilitated within reasonable limits.
Please be honest with yourself about your anxiety and seek help.