Well! I had my first follow-up visit with my doctor, and got my first blood labs. I was right! The lithium was making me
excessively miserable because I was at toxic levels: 1.24.

Ha! (the Ha! is directed to my doctor who kept saying, oh, just hang in there, the side effects will go away). Sure they go away - when I DIE from the toxic levels!
Anyway. Now I've dropped down the topamax (200 mg to 100 mg) and the lithium (900mg to 600mg) so I'm patiently waiting for them to work in happy little synergy. So far I have a smaller headache, I'm less sedated, and haven't had any manic ups. My depressive downs have eased up since i got off some of the lithium too -- that was the scary part, having the suicidality reappear after all these years (and all these drugs~!)
I guess now I'll just sit tight and wait for the next part of the roller coaster. I'm a "rapid cycler" so I shouldn't have to wait too long to find out if lithium will help...