Sorry I haven't read your other threads but rest assured, they all say this. Especially the ones who haven't been bothered previously.
Can you seriously imagine him wanting or being capable of doing full time babycare for half the week?
It's all he's got to threaten you with now that you've told him you're not putting up with his shit anymore.
You do have to accept that if you split up there will be some times when your baby will spend time with their dad, but if they're still young it won't be overnight for quite some time, as I think it's generally accepted that young babies need the consistency of a single primary carer.
Once they are older you may end up having to consider alternatives, but believe me, as a single parent you will come to relish the odd day off, despite the heartache to start with. 50/50 is still quite unusual and even given the saving in maintenence payments, many dads who have previously been uninvolved don't want to take on that level of responsibility for their DCs. If they were interested in being a hands on dad they would already be doing it.
If it does happen, bear in mind that most of us end up sobbing solidly the first night the DCs are away. The next time it's still empty and sad, but a couple of weeks later you get used to it, plan nights out and enjoy the peace. Three years on and I love my DC free night each week and have a gorgeous and attentive man to spend it with.
Don't let his threats paralyse you into staying put if you're unhappy.
if there's honestly anything to salvage it might be worth trying counselling, but it's a long road not an instant fix, so it's important to find the right therapist and to make sure you feel like it's going somewhere, not just stringing you along rather than letting you move on.