I’m not keen on 1/, because generating crazy amount of arbitrary ShortURLs will eat up short URLs for no good reason (also, pretty sure this would be throttled).

2/ and 3/ are actually the same really − because 3/ could be made using a template too ;)

Does wikidata have a limit on how many templates can be on a page?

In the brackets you already show the number of items with this property. Hyperlink that. The second link for the negatives could also be in the brackets as a count, so it might look like "86.56% (2300:357)" where both the 2300 and the 357 are hyperlinks.

Or if that is too much, scrap the counts entirely (a percentage is already clear), and add two links with the symbols + and -. So it could end up simply as "86.56% (+ -)"

In T224001#5204015, @99of9 wrote:

Or if that is too much, scrap the counts entirely (a percentage is already clear), and add two links with the symbols + and -. So it could end up simply as "86.56% (+ -)"

Yeah this is what I was thinking: do a return after the percentage with the number and the +/- or something like (=/≠ ).

I've made progress on this. The page already calls a template ("Coloured cell") per cell, so my concern about template limits is irrelevant. So I decided to go with your "option 2", and made a helper template to generate these links. It has been set up as a wrapper for Coloured cell.

The template: https://www.wikidata.org/wiki/Template:Integraality_cell
A test case: https://www.wikidata.org/wiki/Template:Integraality_cell/test

Note that each cell now needs 5 parameters instead of 2:
{{Integraality cell |
1=(number between 0.00 and 100.0, as currently supplied to Coloured cell)|
2=selector_SPAQRL|
3=grouping_property|
4=group_item|
5=column_property
}}

In each case it's ok to have spaces in the values of parameters, as they will get encoded. It will probably break if there are ever pipes or curly brackets in a parameter value.

Looks good, thanks.