If the table were turned, no one would even suggest that maybe a lady should stay with a man who shoves her from behind, slams her laptop shut, and barricades her in the basement. No one would suggest reading a book to make the relationship better.
Not that it should be much consolation, but they do. I just spent several months -weekly meetings- in a group of women who'd been abused. Women showing up with fresh bruises. Etc. All of us had been told by plenty of people to stay. They were wrong, but they -counsellors, family members, highly intelligent business people- sure did tell us to stay, to read the books, to try new techniques ourselves in an attempt to prevent their outbursts, to empathize with ("understand") the abuser, give the abuser time, look at it differently, and so on.
Something I find helpful: Statistically, most people will leave an abusive relationship about 8 times before they finally leave for good. There are lots of reasons this is so, but it's helpful information for (a) helping an abused person not feel so silly through the process, and (b) giving their supporters more patience and acceptance while the abused person goes through the process.
+1 to Lundy Bancroft's
Why Does He Do That?.
Also, it can indeed be terrifying to think of being alone, but it's not that the options are "be happy some of the time with a person who is usually lovely but sometimes abusive" or "be alone, isolated, devastated, depressed, and eternally grieving". And the third option isn't always just a better partner. Find out what -besides a partner- makes you happy, and pursue
all of that. Then, whether you have a partner or not is entirely moot for you.
Finally, almost every person who is abusive is usually lovely. Otherwise, very few people would be in a relationship with a person who is abusive. The loveliness is required for the abuser to maintain their option to abuse.