CVT oil - how necessary is Nissan NS-2? How much if you remove the pan?

In another post, I mentioned that I have a 2011 CVT Cube that is sluggish on takeoff. Took it to a mechanic who eventually diagnosed a low-speed rubbing noise as coming from inside the transmission. We thought it was a wheel bearing. He also managed to trigger an obvious transmission shudder. At that point, he said "Nothing more we can do; this is going to be a $4000 transmission job."

But I've seen videos that replacing the fluid can fix these problems even when mechanics say a new transmission is needed.

So I tried replacing the existing fluid (which was pretty clear) with FRAM fluid, which lists NS-2 as a compatibility along with many others. FRAM the only one they had locally. But thinking about it, FRAM looks like a universal fluid that might not be as tuned for Cube as the real one. After the fluid change, the noise might have changed a little bit, more a drone than a grind now. I found takeoffs to be a bit more zippy, but still some sluggishness and hesitation (slip?) while accelerating uphill.

So my questions are

• Do I do another change with genuine Nissan NS-2 or maybe Idemitsu (just $50 for a gallon)? Is either one better? Is NS-3 potentially even better, as I've read here?
• I'm thinking of dropping the pan this time. Is it possible to clean the mesh filter and replace just the paper part of the oil filter? Or do I get everything new?
• If I drop the pan, is the amount of fluid a lot bigger? Just draining it gave about 4200 ml, and refilling went to the top of the hatched region on the dipstick. The official capacity is 7.4 liters (TM-234 of 2011 Cube service manual). It seems implausible that another 3 liters would be released by dropping the pan. How much fluid do I need if dropping the pan?

I want to try everything reasonably cheap and simple before resigning myself to a car with a dying transmission.


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edit: I looked up the MSDS of FRAM CVT fluid and it has a viscosity of 33.0/7.2 at temperature 40C/100C while Nissan and Idemitsu are 26/6.25 (see this video); FRAM is like AMSOIL (34.9/7.3), and only Castrol is a little bit more viscous. All are more viscous than the official Nissan fluid. I think that viscosity is what prevents slip, so maybe FRAM is actually better than Nissan or Idemitsu for a bad transmission, though I suspect fuel efficiency will suffer. The spec sheet for AMSOIL looks a lot like FRAM but differs in the flash point, and the car compatibility list is very similar in content and phrasing, so I think that FRAM might be rebadged AMSOIL. The price similar, too (half that of Nissan). From the video, AMSOIL might be better than Nissan (which is apparently rebadged Idemitsu), based on their 100K mile CVT belt wear tests in taxis. So I think that fluid-wise, my car might be as good as it can get, and genuine Nissan fluid might be a downgrade. I suspect it's an issue of belt wear.