To reach out to my DH's ex to see if he was abusive in their relationship?

Contact the police, ask for a Clare's law disclosure. If he has a history they should be able to tell you. You should be able to find details for how to apply on your local police website.

No. You shouldn’t.

Let’s assume he was. She has left and moved on. She likely doesn’t want dragging back into anything to do with him. That could be really distressing for her. And then you choose to stay anyway? So she lays it all out for you for your own piece of mind? What about hers?

and what if she says ‘no, we were just really bad together. He is a good person deep down. We both behaved badly and brought out the worst in eachother’. How is that going to make you feel? It’s a risk you will end up feeling worst.

Or worse, what if she contacts him to say you contacted her?

You’re not crazy OP, he is abusive and I’d say it’s almost certain he was also abusive to her.
The behaviour you describe is abusive and it’s not a great environment for children.

You don’t need to speak to his ex. You are not crazy.

You need to leave OP. Imagine spending another 5/10/15 years with this man and how damaging that will be for your kids.

Make an exit plan and don’t tell him until it’s all in place. Explain everything to your kids as best you can. Is he safe enough to still see them once you split?

No harm in messaging her but you might not get a response. You don’t need the validation either.

My ex husband’s new wife contacted me to ask the same question. I supported her while she left him for abusing her the same way he did me. I think speaking to me helped her leave quicker

I would say no tbh. You don’t need validation that he is abusive, you know he is abusive. It’s hard though because you are being manipulated. Directly and indirectly through your children. I would strongly recommend doing the freedom programme through woman’s aid.

You don't need her validation. You aren't going crazy.

Having said that, if my ex's new partner reached out to me I would be happy to reassure her it wasn't just her. I have wanted to check in the whole time they have been together but it didn't feel right to in case he had changed

No. If your husband is verbally abusing you and getting drunk all the time, that’s all the ‘validation’ you need. This relationship isn’t working for you. Figuring out the financial stuff is harder, I know.

You can ask but you might not get a response. You might also find she tells a friend to tell him to get you to never contact her again. Letting the cat out the bag.

Could you not do Claire’s? Or Sarah’s law I forget which one is which on him, if police where called there could be a record.

He probably was but even if he wasn't, how does that make your situation any better?

I wouldn't. It doesn't matter if he was an angel or asshole to her, he's abusive to you.

Could you go stay with your mum?