Is C/ FB really Zam's worst moveset?

No, C/SB is. At least focus blast is super effective against a lot of enemies. I actually like focus blast :)

Being SE makes up for lack of STAB

On paper against a neutral enemy, yes. Psychic and fighting don't synergise particularly well. However, since the 'neutral enemy' Blissey and Snorlax is actually weak to focus blast, then it becomes very good indeed.

Alakazam worst moveset is HP

All of Alakazam's movesets are solid provided you don't get Shadow Ball. Future Sight is the highest DPS psychic charge move in the game, Focus Blast hits many prominent defenders super-effectively such as Blissey, Snorlax, and Tyranitar. Shadow Ball sucks because Blissey, Snorlax, and Tyranitar all resist it.

I won't power up a ShadowBall at all...but I use FocusBlast a lot.

Worst moveset against the majority of defenders... maybe
But there's only 7 defenders in this game..and FB is best against blissey snorlax and maybe tyranitar