I did want the ending to be sort of sarcastic and understated
Be careful with sarcasm, you can't always wink at your audience. The best sarcasm is also GOOD. Most sarcasm is brutally obvious, like the Bartok Concerto for Orchestra, but I don't think that is as funny as I used to after I read Shostakovitch's book.
As for Sibelius, I have tried converting the piece to a midi sequence and transcribing it through Sibelius but too often it fails at doing more than two voices at once automatically (as differencetone said). It could be the midi itself that could need work (e.g adjusting note lengths), but the solution I have tried so far is to use pencil and paper and transcribe it that way (though it is tedious). Will try Digital Performer.
The problem with DP is that you can't edit the notation. Transcription of piano music is always a pain. I use pen and paper and re-write as I go, and then just input. But you don't transcribe just for fun, you do it for a performance opportunity or commission. Otherwise you just leave it as MIDI or audio. Even a film composer won't bother with a score unless he is using real instruments.
And how painful it must have been for the classical composers to actually compose their music note by note and write it on their score (even more so if they did not have access to the piano)!
Life was slower without computers, only 30 years ago! My son, a violinist, didn't see hand written manuscript until he was seventeen! ("Dad, the parts are, like, scrawled out by hand!!!") Imagine life without recorded music! Imagine life without antibiotics, it throws a different light on Romanticism! Imagine having children with a 75% infant mortality rate (19th century!) Things change. Also, once you start writing music from scratch, you may actually find the piano a hindrance.
over the years my views have changed dramatically due to my being more acquainted with certain forms (like the fugue), and admiring them due to their great logical rigor (which exudes a hidden beauty, in my opinion). I would love to try my hand at planning on a higher level too, which is what improvisation seems unable to offer; I am aware that certain short phrases and musical motifs can be incorporated gracefully through improvisation, but not harmonic movement and progression, which is central to the works I admire. It might not be as fun, but perhaps the above could provide something new.
Writing music from scratch is well worth it (for appreciation if nothing else!). With improvisation, you work with something that is already there - you transcribe, then stitch, smooth, sand, reinforce etc. With composition, you start small and build. Because you are always working one note at a time, the trick is to always know where you are in the structure you're working with. Start with a simple form, like ABA, and then build the material for the A section. Always draw your "new" material from some aspect of your old material, and keep in mind what your small scale and large scale structural functions are. Structures are hierarchical, so you need to keep track of what you are doing on several levels. (You do this subconsciously while improvising.) After writing your first phrase, model your first section on your first phrase. Model your secondary keys on your harmony, use the timing as a small scale model for a larger structure. Always know where you are going and how far along you are. Then use the secondary material to form your B section, which you also build. When you return to the A section, realize it is a consequent to your original antecedent. You are coming home not leaving. Use a coda to tie up loose ends. Make it as tight as possible. Then go back over everything and add more originality! The frame is done, now do the interior and exterior decorating! It does no good to hurry, the journey is the point! It is like practicing, it takes time and patience. After that, you may wish to arrange the piece for an ensemble, and you then re-imagine it and add more stuff! You can derive a lot of fun and satisfaction from the process. If you want to write music, go for it. When you are done, you will that much better at improvising! Best of luck -