This doesnt have much to do with husbands who were abused but maybe it will help a little anyway...
I guess my thought is if he is acting out in this way & you already know he was abused, why you would be asking about signs?...maybe i'm just a little dense this morning
I know there are MANY different signs you can look for in an adult that would (but not always do) indicate childhood abuse. Any type of substance abuse, anger, withdrawal, depression, any & all types of sexual dysfunction, risk taking behaviors, obsessive compulsive behaviors, worthlessness, these are kind of the tip of the iceberg, the things you might notice without having to dig very deep.
I do hope you are able to convince him to get help as it does seem to be escalating. But you need to know that if he doesnt want help, thinks there's no problem, you need to take care of yourself. Remove yourself physically from the situation if that's what you need to do to keep yourself safe.
As for why he would just now be losing it after all these years....it just happens that way sometimes. Think of it like a dam that has a crack in it. It's done its job for a long time holding all the water back but over time the crack gets wider & wider. Pretty soon it's a flash flood & there's no stopping it. He needs help. I'm not a battering husband, but the same scenario applied to my abusive childhood.