AW2725DF - Issues with custom refresh rates

[twigs]

TLDR: Unable to lock in any non-standard refresh rate via CRU and circumstances do not enable G-Sync to do so either. Am I stuck hoping for a firmware update regarding DSC or are my approaches and understandings wrong?

Hi, display noob here, I'm trying to "sync" my fps, refresh rate, and peripheral polling rates. I hadn't done the most research when buying this monitor and had been entirely unaware of DSC or any limitations I'd run into - this is a significant speed jump from my peak experience with the AW3423DW.

My primary focus is syncing 250hz with Quake Live's 250 fps cap, though I'm thinking I'd generally run 333hz for other games as well. (These values divide well into peripheral polling rates which are multiples of 1000, reducing jitter)
I'll go over what I've tried so far, note that I've never touched CRU before.

1) Basic Utilization of G-Sync
The frame rate limiting in Quake Live is quite poor and unstable, as a result the variable refresh rate is bouncing all over the place in a range of ~200 to ~330. Quake Live itself can specify refresh rates, however has an upper limit of 240hz, so I'm stuck with using a value of 0 which reflects the external refresh rate values.
So far, in my experience, this is providing the best experience in spite of the variance.

2) Create a 250hz custom resolution w/ CRU
I haven't been able to get any CRU changes to reflect in any way upon restarting drivers. I'm being told this is due to DSC being forced on with the monitor, however I haven't quite clearly came across DSC being a total blocker for CRU working in some searches.

Since I'm a noob I'll describe my process, unfortunately I can't post images: I followed this guide on QFT to support faster transfer speeds for a lower refresh rate on high Hz panel. I added a resolution with 2560x1440 @ 250.029 Hz (1690.00 MHz), 621.323 kHz horizontal to the DisplayID 1.3 extension data block.

3) Limit the variable refresh rate range
Since I can't specify 250hz in game or any windows/nvidia/monitor settings and observed a wide range of rates when using g-sync, I thought I'd try to limit the range of rates g-sync could utilize. However, as per item 1, I could not get these changes made via CRU reflected after restarting drivers. I'm not entirely sure how to check the variable refresh rate range that is actually active, but had the same results as my first attempt just enabling g-sync.

[jerro99229]

Same issue, trying to get 1920x1600 with 360hz. Is it even possible with this monitor ?