I personally wouldn't ride it - the severity of rust around the joins is far more than my comfort level. I suspect at least one of the joints is compromised if not multiple. You could try sandblast and oxalic acid bath but only if you intended to keep it.

That said ... I know the little bits (like the nuts on the brakes) are very salvageable. Go to Amazon and get a small container of Evap-o-Rust. Get a small mason jar and fill it an inch. With a wire brush, brush off the brunt of the loose rust - no need to go overboard. Then toss the parts in the mason jar. Leave them fro 24 hours, take them out and rinse well with water, brush and dry. You'll be shocked at the results. Reassemble and enjoy.

Mother's Mag & Aluminum Polish will take the tarnish off the aluminum parts and get them gleaming with very little effort.

EDIT: You'll be shocked what Evap-o-Rust will do to resurrect that headset too ...