It's not always that easy, QE, often the abuse starts out small. Drip, drip, drip.
It can start so small you don't realise it is happening until you are already worn down by it. An insult here, a tantrum there punctuated with lots of flattery and apologies and hope that man you thought you knew is still there, if only you do X or stop doing Y, things will go back to how they were.
Abusers are very clever like that. Leaving can seem impossible. You are so exhausted by it all you don't have the energy, not to mention that it started so slowly it has become your normal. You're not sure what is abuse and what is typical of a healthy relationship anymore, you're not sure whether it is your fault, his or a mixture of both.
I can fully understand OP feeling like she has no choice but to stay until X happens. It doesn't feel as bad to OP as it. She's probably drawn an imaginary line in the sand and when he crosses that line, she will leave, except he won't jump, hop or skip to that line he will crawl to it, slowly, giving OP just enough hope to cling onto that she will move her line, without even realising.
Abuse, especially EA is insidious. It can take away your sense of self. You become a shell of what you were and you can't work out how to change it. Making small choices such as what to cook for dinner becomes an exhausting task. There's nothing left to make a big choice like leaving and it's not that bad anyway because the abuser doesn't X, by the time he does do X, X doesn't seem that bad anymore because the abuse is so ingrained you stop noticing a lot of it, it becomes normal.
It is possible to leave. If OP seeks outside help from CAB or WA they'll help her see her options more clearly, but only she can find the strength to do that and it won't be easy. I can guarantee from personal experience that that first step is the hardest, once she has found the strength to ask for help to leave, the rest is relatively easy, but taking that first step takes a lot.