Piano reduction of a string quartet

[avanchnzel]

I'm meeting a flautist tomorrow to try the last two movements of Mozart's Flute Quartet in D major. As you can see from the title I'm replacing a string quartet. We've performed the first movement in public already, and I barely got by with all the thirds and the most awkward counterpoint I've ever played on a piano.
The finale is a nightmare of repeated notes, stretches and huge jumps along with the thirds and horrible counterpoint. I can do those at quite a tick but honestly, the required tempo is 140. I have to play consecutive thirds and repeated notes. In semiquavers.
This flautist is going to pay for my carpal tunnel surgery.
The accompaniment is really quite a work of art itself and would have been lovely to play at about half the tempo, but that's not what should happen in the original. I'm not exactly Martha Argerich, so would anyone have any ideas on what to do without completely rewriting the accompaniment in a more pianistic way (and thus losing the character of the piece)?

[keypeg]

I think it might be easier for people to help you if they had the actual score.  It's not my expertise but I found a link in IMSLP to get this going.
https://imslp.org/wiki/Flute_Quartet_in_D_major,_K.285_(Mozart,_Wolfgang_Amadeus)
Here it is played with piano accompaniment (maybe gives you some ideas?)

as a quartet

(If this is to pay for carpal tunnel surgery, you don't want to strain your hands even more.)

[avanchnzel]

I think it might be easier for people to help you if they had the actual score.  It's not my expertise but I found a link in IMSLP to get this going.
https://imslp.org/wiki/Flute_Quartet_in_D_major,_K.285_(Mozart,_Wolfgang_Amadeus)
Here it is played with piano accompaniment (maybe gives you some ideas?)

as a quartet

(If this is to pay for carpal tunnel surgery, you don't want to strain your hands even more.)

Hello there, as I said we've already performed the first movement in public and minimal snipping has sufficed to keep things together. The real problem is in the final movement, and many of the figurations are impossible to play at the speed of the actual quartet recording on the piano.
I have just met the flautist to practise with her and she's still learning the piece, so we were able to practise it at a slower tempo. As time passes maybe I'll magically acquire the technique to play more of the arrangement (which is by Heinz Stolba, whoever he is) and so some surgery.

If anyone has other suggestions and/or are familiar with the piece, please feel free to drop in.

(Thankfully so far this is not to pay for carpal tunnel surgery yet - anyway healthcare here in the UK is free. I actually injure myself periodically but hopefully it won't come to that.)