Have you at least gotten a police report filed in your jurisdiction? if so, request a copy and send it to OKX so they know your case is in process and perhaps try to request for an extension as well. If you're from US or UK, maybe there's a way to file online too.
If you can't get ahold of authorities after that, try calling or going over the counter because there is a good chance solely writing to them will get you inboxed for some time as it is safe to assume they are receiving a lot of complaints hence the mentioned suggestion will land you better chances.
The sad reality is they have limited resources hence prioritize cases. If memory serves right, I remember reading an article about an FBI officer saying there are a lot that are too insignificant for them to look into. However I do think you have an edge since the perp is using custodial CEXs and the small number of addresses mentioned (perhaps the tip of an iceberg) have transacted with big amounts which I highly suggest emphasizing.
I filled in a report for my local police a long time ago, a couple of days after I was scammed. OKX wrote me an email 5 days ago that they froze one scammer's account for 7 days. Will see what will happen next.