You might ask your sister to find out if you can get an escort onto the plane and if you need to switch flights. When my child traveled to see my ex-spouse, he paid for a guardian --employed by the airlines--to do this. I don't see why they can't do it for just about anyone who needs a little extra help getting around an airport, onto a plane, onto a connecting flight, etc.

Also, if you are easily overwhelmed by being presented with grand plans, when your sister gears up, you could gently say "I need things presented in smaller chunks" -- and remember you will likely have to repeat this. I think your plan to finish school and get a job sounds good. I don't see why you can't do this while living with or near your sister.