My dilemma is..my fiance wants to push our marriage date forward, to next year. I proposed to her in a monogamous situation, and it was for commitment purposes.
You could say "No, thank you. I don't want to set that date for a wedding. I proposed to you under monogamous conditions and conditions have changed. Let's wait and see how we handle one big change at a time rather than piling on another one on top and making stress for ourselves."
I'm a fan of long Engagement. When you propose, you propose to you dating partner that you enter the Time of Engagement. And the purpose of that time is to reflect and prepare for marriage. Why short change yourselves on that? Could take pre-marital classes at your house of worship, county extension office, or online to help you prepare and make sure you are talking about all the things to need to be talking about.
Because if it turns out in the Engagement time that you come to find you are NOT not compatible? You can choose to NOT GET MARRIED. Better a successful engagement
that concludes "No. Not compatible after all" than a botched/rushed/short shifted Engagement Time leading toward a wonky/unstable/doomed marriage.
To me it sounds like you have other future plans you want to complete before marriage. Like college.
What are my options? Do I leave my fiance's home next Spring and live off-campus and go to school with my new partner and continue to grow myself, instead of enjoying someone else's accomplishments? I need to be in a safe position if either relationship were to fail, I don't want to be homeless of course.
Who is paying for college? Just you? You working + grants/scholarships? That kind of dictates when/where you can go and how to support yourself as a student.
I'm glad you are thinking about that kind of thing.
And you are right -- you want to be financially independent so if it turns up with you single, you can support yourself and STILL be ok.
I would suggest that at 20? You keep your options flexible. Enjoying being engaged but don't go deeper than that til you accomplish college and whatever else you want to explore as an unmarried person.
Life is long -- you don't have to be rushing through it and cram all your adult experiences packed into the first decade of your adult life. You could choose to spread them out so you can savor them.