I agree with making your own space downstairs
I loved the "Tidying Up" book Mango mentioned, and now Marie Kondo has her own Netflix show if you wanna see her tiny self in action
Purging that stuff downstairs could be very cathartic, and unleashing your creative energy on building yourself an amazing retreat with some paint and free furniture is taking empowering action in a tight situation.
Once the clutter is out, and the bug spray applied, and a good heavy cleaning occurs, you have a palette to work with.
My husband and I both have our "rooms" and mine is in the basement--yes, some bugs and it is colder in Winter, but going down the stairs I enter
my kingdom and love having a place of my own. (In Summer, it is cool and refreshing and I like to go there to rest and read a book).
They have amazing cheap efficient space heaters now--some of which look like little gas fireplaces (not really gas but good electric fakes) which would make it cozy and warm.
Imagine a nice overstuffed chair, a flickering "fireplace", and a cozy bed with lots of covers and pillows to snuggle in.
Pick a lovely shade of paint in a color you love and he hates, get some nice incense, candles, and books, puzzles, adult coloring books, etc. and make a place of peace and tranquility.
You deserve it Wamama