I usually design for up to 270V RMS before clipping starts just to allow a bit of headroom. I’m not sure basing it on your one specimen in the lab is a good move. There are a bunch of “supported” VTs, and I’m really not across all of them, and what voltages they output in various countries. Check out Robert’s reports on them all to determine worst case (i.e. highest voltage with a grid running well higher than spec).
Or @Robert.Wall might have a good rule-of-thumb for a suitable V divider for a 3.3V system across the range of VTs. Come to think of it, the OEM team have been using 3.3V systems for quite a while now, so unless you think they got it wrong, you could just stick with their divider ratio.
Speaking of clipping… it looks like you only have protection diodes on the negative swing on all the analog inputs. You may want to look at adding them for the positive swing as well.
I didn’t find much discouraging news in there:
At 2.5 kHz the amplitude error had risen to 3% whilst the phase error had increased to 10 degrees.
If I’ve done the arithmetic correctly, your 1744 Hz cut-off would turn that 3% error into a 36% error. The reported 10 degree phase error at that frequency doesn’t matter at all - phase error only matters when you’re calculating real power. There’ll be no significant contribution to real power up at those frequencies because V is so close to pure sine wave, so the dot product effectively filters out all the harmonics in I for that calculation. Regardless of how distorted your I signal is, real power pretty much all happens at the fundamental, with the tiniest bit leaking in from the harmonics if your V is a bit distorted (flat tops etc).
The symptoms you’ll see if you filter too hard is an under-read on Irms and all the readings that derive from it: apparent power and power factor (over-read), but you’ll need a very distorted load to see it. You can see a few pics of my most distorted circuits here. That’s probably as good a starting point as any to decide how high you want to go. The CT seems up to the job whatever you decide.