Hi, a couple of suggestions:
a) More exercise...long walks, daily play or training sessions...it's harder to be obsessive when you're tired! Poodles are smart dogs; so engage his mind with fun training exercises to keep him from obsessing about other stuff.
b) Flower essences could be extremely beneficial in Cody's case. I'd especially think of Obsession Remedy to help with the both the intense marking behavior as well as the attention-hog aspect.
c) I'm assuming he is neutered; but if not, that is a big contributor to the need to mark. After so many years and such an ingrained habit, though, neutering probably wouldn't be the only solution.
d) Giving him any attention when he demands it only reinforces him being demanding and makes him the boss, not you. Attention should only be a reward for *good* behavior--sitting quietly, for instance. When he becomes demanding, turn away from him, ignore him...give him attention only when he settles down (which he will do, probably fairly quickly, when he realizes his behavior is not getting him what he wants).