Also, don’t forget to check out John Talbott (bless that man). He provides crucial boots-on-les-champs intel about the latest and greatest in the City of Light.
Septime is not that difficult.
I think online reservations are made about 30 days ahead, so if you remember to make it exactly 30 days before you should have no trouble. Check their website.
I also like L’ami Jean and Le Chateaubriand. Consider Pages restaurant as well.