I'm sure you know this but mentioning it just in case - pelvic floor physios also do a lot of work on diastisis. What you're describing is pretty significant diastisis so I'm sure physio wouldn't fix it but perhaps it would help a bit, if you haven't tried it yet? (And if you can afford it...)

I did ask about physical therapy but the OB said with that size there's not a whole lot that would help aside from surgical repair. I've still been trying to rebuild some of my strength but it's not been great.

The thing with trying on your own to rebuild that strength is that a lot of ab exercises actually worsen diastisis. (I'm a midwife and what I tell my clients as a general rule is if your abs pop out when you're doing ab exercises, it's worsening the diastisis. You want to aim to sort of tuck your abs in while doing exercises. But I'm not sure how easy that'll be with your degree of seperation.)

OBs are surgeons above all so personally I would still try physio if you can! But I would go for a pelvic floor physio as the pelvic floor and abdominal muscles area closely related and affected by pregnancy.

Best of luck! I hope you figure something out that works for you.