I think I used the two polishing grades of novus (either #2 or the slightly more aggressive #3). I don't think I even had the cleaner (that's the novus #1)
It sounds like your scratches may be too deep to get much of a result working for a reasonable effort by hand. You can go back and forth, or in circles, it shouldn't matter. I'd tend to go back and forth as it will help you monitor progress better.
It might be that the "abrasive sponge" (sandpaper sponge?) you used was too course, and to get good results, you'll need a finer grade sandpaper before you can polish. Do you happent to know what grit abrasive/sandpaper you used which caused the scratches? If you do, post it here but basically you'll want to go progressively finer, in potentially multiple steps, until you get to a fine enough texture that you can switch to the novus #3. If you don't know what grit it was that caused the scratches, the next most aggressive thing to try from the more aggressive novus (the novus #3 ) might be something like 2000-3000 grit sandpaper, wetted down (and kept wet) with water as you go. Do your wetsanding from side to side until all the original appearing scratches are no longer visible, before hitting it with the most aggressive novus (which would be the #3) in a back and forth direction perpendicular to the previous last wetsanding step. As a general rule of thumb, you only want to get as aggressive as you need to correct the defect. But in this case, the novus # applied by hand apparently isn't aggressive enough, so you'll want to step it up.
If the 2000 grit doesn't seem to be getting rid of the original scratch marks, then go more aggressive, like 1500. (And if that still isn't enough to get rid of the circular scratches, then even courser... 1000, 600, 400). If doing this by hand, you will need to put in much more effort and also probably use more steps than if you had the power of a machine, but you can still get a good result. Once you remove the original scratches, you'll need to work your way finer, through the steps, as I describe above.
Hopefully the wetsanding materials will be available where you live! If not, I think pieces of sandpaper would easily and quickly ship via air.
If you get full sized sandpaper sheets 8.5"X11" or so, fold and/or cut them into hand-sized pieces by the way, before you use them.
Like I said before, the novus worked amazing on some hard plastic taillight lenses in virtually a single step, but that was using a very powerful benchtop buffer and applying some pretty significant pressure also. It was pretty amazing how well and quickly it worked though - and the plastic looked newer than you'd see on most new cars. Usually, you need to put in a pretty good amount of effort and steps to achieve this sort of "transformation".
If you were using a machine, you might have better results without having to resort to wetsanding. However if you are just pressing against the unsupported window, you are limited in how much pressure you can apply. And you will want to keep heat low if you do use a machine (overheating the material will not possibly come up as an issue if you polish or sand by hand). Good luck - I hope if someone else has done what you're doing, they will chime in! To periodically apply water when wetsanding, a spray bottle will be helpful.
The novus is actually quite fine so going by hand, it may take a really long time to smooth through relatively course scratches. It's good you noticed the appearance becoming more optically transparent, though - this is really what the novus is made for and good to know its doing something! Wetsanding won't go fine enough to give you that result. Eventually, and with persistence, I think you'll be able to fix this. Good luck!
Linear Mode
