Just to put another perspective forward, could it be that he is struggling with family life, after spending quite some time trying to fit in with your set-up he is now sensing that his life would be simpler without someone else (& their child) to have to consider all the time? This new work arrangement may have opened his eyes a bit.
At his age, without having DCs to worry about, it is probably quite daunting to be faced with the prospect of being a step-parent to a young child.
And yes, he should have thought of that before getting involved with a mum, but in those first few months anything seems possible, everyone is on their best behaviour. It's only further down the line that the step-situation and all the logistics of that can become a bit fraught.
Nobody said that every relationship has to end with living together and marriage. There's no reason if you were both happy, that you couldn't have a 2-3 times a week meet-up indefinitely. Similarly, there are plenty of couples whose finances remain separate when living together/married. I couldn't do it, but I know that many do.
However, if it's not what you want, then it won't work.
FWIW, my DP just took me & my 2 DSs out for lunch and insisted on paying for us all (as he always does) even when I offered. He likes to treat us all, and while he sometimes accepts my offer, he knows that I don't have as much money as him and will subsidise me so that we can all have a nice time together. In my mind, that is what a caring partner does. (I also sub him if he's short at the end of the month and I'm not and I buy him toiletries/food etc when he's at my house, it's give and take.)
If he was penny pinching I would think less of him and I think it speaks of a generous soul, he is also very giving with love and attention/time as well as cash. Someone who doesn't think you worthy of sharing his money and wants to claw back time from you too is not worth investing your emotions in.