I love how proactive you are about your room! You’ve got target areas you want to fix and ideas about how you want to go about it, which is great!! It’s so much easier to tackle a room when you have plans about what areas and aspects to work on first.
That being said, I really agree about painting the walls! White or a shade off white in any color family (think the lightest possible blue, the lightest possible grey, the lightest possible tan) would not only open up the space and make it seem bigger, but will lighten it up tremendously.
I love the idea of a tapestry at the top of your bed, especially since you have such a large and specific space to fill (so finding or making custom wall art could be tricky or expensive.) Sites like Urban Outfitters or Society6 are great places to look since they have a lot of different prints and patterns that you can choose from to get exactly the look you want!
As far as your vanity, what about upcycling it?! I recently redid the sideboard in the Boffice, and while you don’t have to go as far as repainting it if you don’t want to, switching out to new, cool knobs could be exactly the touch it needs!
Hope this helps!