But what does my audition repertoire have to do with any of that? Isn't it just to show that I can study at the university level?
Yes, the primary reasons behind your audition material is to see if you have the stuff to succeed in the program. However, in the perspective of personal development, knowing what your future focus will be will allow you to prepare early for it. You can use your current audition rep as a launching point for future endeavors. Planning early will also help you focus your efforts and in the long run may save precious time in building repertoire. The importance of economizing work will become very apparent as you progress through your degree.
It sounds like you have broad interests in music and are well on your way to becoming a well rounded musician. I am particularly pleased to hear you are interested in improvisation. U of T's program tends to cater to people with an intense focus on a particular aspect of music, ie. performance, teaching, composition, musicology, etc. However, if you are someone that would like a bit of each the rigidity of the program could prove frustrating. Not all universities have programs that require you to follow a strict path in specialization. It is something to think about. Of course you could supplement your university education with private lessons and non-degree courses in the subjects that interest you.
If you understand U of T culture and think it will benefit you - it looks like you have a very good idea of what you are getting into - then by all means go for it. I know it is difficult to fully understand student life at a particular university without having walked in those shoes.
With regards to your concerns in public performance: you need to play in public more, it sounds simple but it's what is needed. Public performance does not have to be formal recitals, concertos, competitions and the like. Play in a seniors residence, hospital, dance studio, church, accompany choirs, and the list goes on. All of these things build up your public performance experience and endurance. You don't even have to play technically difficult music, just aim for playing well in public and enjoying the experience without undue anxieties.
Another thing you could do is record yourself. Pretend it is a performance and make a journal of your recordings.
Speaking to your program, I do concur with Visitor about the romantic selection. This is one place you could use to display your technical aptitude.
If you are uneasy with 20/21st century music, you could go with a character piece - something that is not too technically demanding yet shows your ability to musically voice a certain character, preferably in contrast with the rest of your program. You have a lot of options to expand outside of the RCM syllabus here and present pieces that are unfamiliar to the jury. Visit the CMC library and explore.
https://www.musiccentre.ca