Welcome here where I'd imagine there are many that will understand how you feel.
Being in an abusive relationship is a hard thing to live with and wears away your feelings of being an independent and capable human being. When you have kids that is an additional problem, you do not want them to see your family life, or think it is normal.
May I ask if he is abusive to them too?
It is so easy for others to day "just leave" and I guess in a perfect world, with finances, support and somewhere permanent to go that might be the case. However it is not a perfect world. You may stay from fear, from love and hoping for better times, from having nobody to turn to, for the sake of the kids having somewhere to stay, to be near work, from sheer exhaustion, or many many more reasons.
Sometimes one can know what one would like to do, but when thinking about it you find it's not really on -at that point your heart does sink, you feel guilty even and wonder if things will ever be different.
I apologize if you have done this already, but if not I'd suggest ringing 1800Respect - 1800 737 732 and talk matters over with them, see if there is support in your area -what it does and importantly and how long it lasts. It also give you perspective, something lost when too close.
I know you wear a mask, most people do,I certainly did (for other reasons). The 'why' can be complicated, pride, not wanting to answer questions, a desire to be treated normally and life go on as before, plus more
That mask is a heavy burden to keep up, and does two things, it leaves you feeling isolated, with nobody on your wavelength, and it shuts off doors so help and sympathy is not offered.
At the moment you do need support, even if you do stay, is there anyone, family or a friend you can talk to without hiding things and feel cared for? They do not have to 'fix' anything or even give suggestions. Coping with all this by yourself is extra hard. and leaning on another does help.
I hope to talk with you some more