....I'm trilling on 2 and 4 because even though my edition suggests trilling on 3 and 5 I simply can't do that fast enough and I don't want to make things unnecessarily difficult for myself.
Of course! IMO 3-5 is completely and utterly ridiculous. I know that the people who do editions are supposedly experts, but.....all I can say is "but."
3-5 is completely ridiculous.
I'll try using 3 on the D# and C#....
Oh OK -- so that means you WERE using 2?
That might well be your main problem with the passage.
But also....
....the only reason this passage is difficult for me is because I'm trilling with 2 and 4 and so the only finger left for the C-natural is the thumb....
Not so! You can slide the 2nd finger onto the C.
And even if you use the thumb, which is what I would do anyway....
....and following that there's no fingers left for the remaining flourish.
Sure there are!! You can easily 'slide' the thumb from C to B, especially because (IMO) the desired articulations leave plenty of time for it.
You've been making it harder than it really is with (a) a bad fingering, and (b) some wrong assumptions.
I'd bet you'll now be able to play it quite well pretty soon.