I went through a very similar situation. In my case, my ex was extremely non-cooperative during what was supposed to be a dissolution of marriage (so technically faster because you should agree on everything) and didn't care about my legal status here, so he wouldn't sign the divorce papers on purpose, causing me to be in a very dangerous limbo for immigration. For USCIS you're either married or divorced. Separation is not contemplated so you have to choose a path if you want to proceed with your ROC.
Originally, when I applied for ROC in 2022, I applied as married but requesting a waiver due to the upcoming divorce. At that point we would have been separated for around 5 months. I wrote a letter, signed by both, that I attached to the ROC papers I sent USCIS, explaining our circumstances, why we separated, why the marriage didn't work and why we were requesting the waiver even if we weren't legally divorced yet. Long story short, my ex became increasingly abusive over time, refusing to cooperate, threatening me not to sign in the (his) hope I would get deported and lose custody of our child, plus other distressing memories I will not bring up. A year after filing though, USCIS sent me an RFE letter requesting a copy of our divorce decree so they could proceed with my application but guess what? We weren't even close to being divorced. I panicked, hard. What was I gonna do? I didn't have money for a lawyer back then, so a dissolution was the only, most cost-effective way for me to deal with it.
Somehow, after I told my ex about the RFE, he had some instances of mental sanity (guilt? regret? remorse?) and finally agreed to sign the dissolution papers. Being a dissolution instead of a traditional divorce, it only took between 60-90 days for it to be finalized, but my deadline to provide my divorcee decree was still beyond our court date. What did I do then? I responded to USCIS's RFE with a letter, explaining the circumstances for not being able to respect the deadline by a couple of weeks, by being completely honest and frank about it and providing them with a copy of the letter court sent us with the final hearing date, as proof we were really close to the end of our marriage. I asked for an act of good will on their part, asking them to be compassionate about my circumstances, and promising I'd send the divorce decree as soon as I had it. After that, I simply waited for our divorce to be finalized (I assumed USCIS would take at least another month to contact me anyway) and all of this worked for me. I sent the divorce decree asap and after three months I received a letter from them (or I simply checked the case status? Can't remember), saying fingertips were applied to my case and I didn't need to show up to renew them as they previously stated in another NOA letter.
Would I suggest to go about it this way? Absolutely no.
Was I "forced" to proceed this way? I think I had no other choice honestly.
Someone asked me why I have not applied under the "extreme cruelty" or "extreme hardship" waivers, but we all know how hard those cases are to prove and even qualify for. Not to mention, at the time I filed the petition, he wasn't even half that bad so I had no idea about what was coming.
My suggestion then, is to file for divorce asap if you have the means to afford it (so she'll have no choice but cooperate, unlike during my dissolution) and convert your petition, requesting a divorce waiver. At most, you'll get denied and will have to re-file, requesting the waiver this time, while working on your divorce.
I am a big fan of letters, they have worked in both cases during my ROC proceedings, but they're obviously not a foolproof or recommended method to try and mitigate the situation. Having said that, I mean that maybe they worked for me but every case is different of course, and what worked for me might not work for someone else. In my opinion though, it's always better to send it and for it to be useless, than not taking action at all.