v9.6.5 looking good.
This is may be a bit on the picky side of things, but I noticed a lot of the blue boxes are a bit too large, and it makes the sheet a bit ugly-ish. Not the end of the world, but I find it annoying.
https://gyazo.com/b7af7ca3d817044264f728621630d8d7
https://gyazo.com/75cccd1c186fc9d3840c0516c660d440
Things like the above would be a lot prettier if the blue area was confined to the box, rather than spill over the black region.
However, where it become a bit more important than just 'looking nice', is when those blue boxes overlap with one another. But also it makes editing the sheet a bit harder, especially when two blue boxes overlap them one another.
https://gyazo.com/173ffbf1622d0829f583e5ba80227fad
https://gyazo.com/e9f8a4cc8b0fc1f660cb802d843f083e
https://gyazo.com/92f740631bb5e3d2475b1db23dfc9332
https://gyazo.com/1c8434b720ce447f617791b2cc27626f
This is particularly annoying when using things in tablet mode, because you don't know, e.g., if hitting the attuned box will tick the box, or put the cursor in the text field.
Short answer: this won't work, because all the text/checkboxes will be wrongly aligned. Making the 'blue' 'looking nice' would make the text look awful.
The form fields are layout as they currently are to make all the things you put in them fit to the rest of the sheet. Either fit the text to the lines (the overlapping fields), or fit the "X" in the checkbox (the checkboxes). Changing the size of the field would change the size and shape of what's in it along with it. Making the checkboxes as big as the white area would make the "X" so small it would just be a dot with a lot of white space around it. Moving the overlapping fields so that they adhere to the lines/box the text has to go in would make the text not align with the lines/box. Moving the top of the field down would also move the top of the text down with the same amount. So the options are: have it work as it currently does or have better looking 'blue boxes' (as you call it, you can make it any colour you want in Acrobat) that have text in the wrong place. I choose the former
BTW, if you don't like how the blue looks, just turn off the colouring of form fields

I don't like looking at the sheet with all the form fields coloured like that, it is rather distracting IMHO. You can edit this feature in the settings of your Acrobat program (CTRL + K and go to "Forms").
Also, for the dual save DCs, here's a mockup for (at least IMO) a better looking layout
https://imgur.com/b7NkQPE
Great idea! One that I had while making it as well. Two problems with that:
1) where do you put the modifier fields so that it is still clear to what DC they belong.
2) when printing to greyscale, how do you understand what score goes with what DC? I see the arrows, but they are really tiny and break style with the rest of the sheet.
But I'll try if I can make something work, because it is something I was struggling with while implementing this feature.
One thing that also is a bit ... unorthodox is calling the thousand separator a 'decimal seperator'.
There are many convention in the world, but keeping it to those that could see use in this sheet, we have
English plain (decimal seperator is a dot)
3132.24
French plain (decimal seperator is a comma)
3132,24
English Scientific (thousand separator is a space, decimal indicator is a dot)
3 132.24
French Scientific / French 'Common' (thousand separator is a space, decimal indicator is a comma)
3 132,24
English 'Common' (thousand separator is a comma, decimal indicator is a dot)
3,132.24
23,132.24
Because most people will use the sheet in English, the default really should be be none, spaces or commas for the thousand separators, and a dot for the decimal. Then in options
Decimal ([ ] Dot, [ ] Comma)
Thousand ([ ] None, [ ] Spaces, [ ] Commas {this option should only be available if the dot option is selected for Decimal Seperator})
I'm a bit taken aback by this post. Why do you think I'm "calling the thousand separator a 'decimal seperator'"? It clearly says decimal sep
arator right? You choose the thing that separates the integer from the fraction, not the thing that separates the thousands from the singles. Note that it only has effect on how the number display if you are not editing the field. You can always use both a comma and a dot as decimal separator when entering data. Acrobat has no option to select a space as a thousands separator, so that is not an option I can offer. Because numbers in the thousands will be very uncommon in the sheet, I choose to have the thousands separator by dependent on the decimal separator (i.e. a comma if the decimal separator is a dot and vice versa). Only the XP and money fields are likely to have numbers in the thousands. Using the, as you call it, 'common' version seemed to me as the most common thing people would want. The only extra option that would be viable in Acrobat would to offer the option to have no thousand separator, but I felt that writing code for that was a waste of time, and I still do.