In the context of the Alamo itself, his forced march through a blizzard to get there cost him eight times the men he defeated, and the battle itself cost at least that many again, if not twice that number.
That is not a decisive victory. I would call it winning a particular battle at an unbelievable horrendous cost that if persisted in and replicated would ultimately lose the war.
Yes, he won...but not decisively so. If anything, the Texans and their allies proved to him how costly his victories would be and in that way won their won decisve triumph in losing that battle.
My criteria for "decisive" is that the defending force was wiped out. But they took a ton of invaders with 'em (on a ratio of about 10:1, IIRC), God bless 'em! I'm not arguing any of your points in the strategic sense. :-)