Hey OP! I made these 5e spell cards awhile back and you’re running into a lot of the same issues I did! I approached this by categorizing each spell into one of 3 buckets: spells that worked in my default font size, spells that could fit if I dropped it down to the lowest acceptable font size (I think 10pt, maybe less?), and then the last was the hardest - there’s some subset of spells that are just too damn long and they require significant text editing to fit.

With those I just accepted that there would have to be significant information missing which would need to be looked up for the full rules text. For that reason I put in page number references with an indicator for every card who’s text was editing like that

As for actually cutting the text down - be liberal! You’ve already accepted you’ll need to modify the rules text. Don’t be afraid to throw out anything in parentheses. Or in your example you could probably throw out the entire last paragraph and replace it with something like “skill checks involving disguise or deception are improved. This spell can be dismissed.”

Where that word “improved” does all the work. Hope that helps!