Hey way to go! Not a bad start! There are some solid arranging chops clear here! Also, welcome! Also, holy crap this is an ambitious piece...
Firstly regarding your idea of the time signature, while I do agree with your logic, in the end I think I'd vote to just keep it to 6/8 3/4. It's common in certain dances (especially some traditional Spanish ones) to have this kind of rhythmic pattern, so I think 6/8 3/4 would be just fine. It would also keep the measures smaller into 6-beats rather than 12. Overall, easier to read; even though you're right. Maybe someone else will come along and disagree with me but that's my thought on it. Apparently we like 3/4.
Other things:
- Text for game title and copyright info needs to be centered. You can do this by holding "Ctrl" and "Shift" and pressing " ' " (Ctrl+Shft+').
- You've got "Arnanged by ANonsenicalValid". Check that typo.
- Double check the sizes for these textual elements as well. They seem small. Copyright should be 10pt, song title 24pt, and everything else 12pt.
- Using the ScoreManager, get rid of the "Pno." at the beginning of all systems after the first.
- The clashing of elements between systems is a problem. You'll need to space these out to give everything its own space.
- I'm wondering if there's a reason you didn't just put the upper voice in the RH staff for measures 1-4. It's not really a big deal (as in I could live with the way it currently is) but I just don't see why not. It would likely look cleaner.
- I understand this is an import from a MusicXML file, so maybe add in some measure numbers every 5 measures or so.
- I'm all for dramatic effect, but the dynamics are a bit more extreme than I think you need. I get that this is super virtuosic, but therefore have a bit of faith in your players (because they'll know what they're doing)- I'd recommend turning the fff down to ff at most, the ff to a f, the pp to a p, etc. That being said, I generally like the dynamic contour you've included.
- Whatever-measure-is-first-on-page-2: Your RH is changing from one layer to another for no reason. Keep this all in layer 1 and then you can beam things more effectively too.
- Many people here like to see slurs connecting grace notes to their parent notes. I think such an element would be effective here.
- Your rhythmic divisions (6/8+3/4) is generally shown in your beaming and rest compositions; this is good. However there are some places where it's not so intuitive. These include RH measures 8, 9, 12, and 17 (connect the triplet to the preceeding eighth notes).
- Part of me wants to suggest helping the intense difficulty of this thing by removing the lower octave from the low bass notes, but the other part of me asks what difference would it really make. It's a brutally tough song regardless, so I'm not sure if it would make all that much of a difference to make this difference. That being said, I think it's still something to consider whichever way we end up leaning.
- One thought similar to the last one that I think would go a long way would be to get rid of the lower octaves in the melody in measures 9-12. The original is still single notes here; it seems strange to me to have it suddenly get so huge in texture (a creativity move, I know, but still).
- This isn't important for the accuracy or aesthetic of the sheet itself but the tempo is playing at dotted-quarter=90 because Finale isn't recognizing the period as an augmentation dot. You can fix this manually by going into the properties of it under the 'Playback' tab setting the function as "Tempo" and doing it that way.
Easily the most crucial thing to take care of is formatting. Get some space in there, fix the text, etc. Then it'll be way easier to pick it apart more specifically. But for a short song there's a lot of content here to look at.