I have read your other thread and I am in awe of your strength and resolve. You engaged with posters, it was clear you were at the end of your capacity to deal with things. I applaud your capacity to act so quickly and with such certainty. I expect this has come as an immense shock to your ex-partner and he is lashing out to try and gain back some resolve. So, look past it, see it for what it is, he feels small, he has to start thinking about what he needs to do for his children and himself - without you there to provide structure, stability and a helping hand. He is floundering and his ego is lashing out.
Some advice from me, take whatever is useful and ignore the rest. Firstly, I have an only child and carried immense guilt at that however, now that my son is in secondary school I no longer beat myself up because the breadth of activities that open up when they get into secondary school is immense. You will both be busier than you know soon enough!
Secondly, well done for recognising that it is the simple acts of kindness (a coffee in bed in the morning) that mean so much and, when removed, communicate so much. You told him this, it was his opportunity to understand and address what was going on in your relationship, he let that opportunity pass.
Thirdly, this relationship might be over, it might not. Not everyone is born into a loving family with emotionally literate parents. Some of us learn the hard way by failing again and again before we become aware. People are complex, life is nuanced, no one is beyond self improvement. Living and coping alone might just be what your ex needs to develop some much needed perspective. Don't rush to respond to his messages; no need to play games but do realise that he is attempting to change the narrative and take back control, you don't need to feed his ego.
Lastly, if the relationship ends, it doesn't mean that it was a failure. Some people are in our life for a reason, a season or a lifetime. Not every relationship, romantic or not, is meant to endure forever. Each one brings something to our life and teaches us something.
I wish you the very best and do not write yourself off at 40, you're not even middle aged yet!