I'm on Arch with i3wm. Arch has support for Flash, and despite its rolling-release nature, I've found it to be reasonably stable for a casual desktop user. Arc

I'm on Arch with i3wm. Arch has support for Flash, and despite its rolling-release nature, I've found it to be reasonably stable for a casual desktop user. Arch and i3wm probably also fit your methodology with regards to being "thin", "bare bones", and minimal. You may want to try Arch out, even if you don't end up using i3wm.