I’ve known companies in this situation try everything from price gouging (“it’ll cost you $10 a record to export your 2 million records”), to just flat out refusing to pick up the phone, answer emails, or reply to legal threats: in principle a court can tell them they need to hand data over, in practice they can drag their feet.
As a former CTO I think you might need help to help you figure out your strategy in more detail and then get it delivered. Plenty of non-tech businesses have dev teams, and it’s becoming more and more frequent in my experience. You can attract a team with flexibility, autonomy, a promise they can learn new things and a great mission. A good CTO with experience in startups can probably help you get that lined up right.