As a signature thing (as is the witchblade), I wouldn't allow you to do this with glamour, that should probably be a human form + claws thing to represent the weapon. Triggering the other form would be conjuring the weapon, but there is no roll involved.
That being said, is there anything acting against your conjuring? If not, don't even bother to roll. Here, you have a sword. If there is, for example a wizard willing your sword away, roll against the wizard. Or against a block on conjuring or whatever. You could easily have a regular sword with you, for the most part, conjuring it is mainly just your style, I guess. A weapon:2 and armor:1 should be no problem.
One of the weaknesses would surely be cold iron. If your conjured sword is hit by one made of steel or anything made out of iron or steel, really, it will shatter into a million tiny pieces. That is, after all, the ultimate faerie weakness. And probably the reason why some of their stuff is made from real materials. A bronze sword might be weaker than a steel one, but it will block it at least a few times.
Though glamour is usually (as in "how faeries use it in folklore") not used in such hands on ways. It's used to dazzle, to swindle, to bamboozle, to finagle. A big weapon and shiny armor to impress and intimidate someone mostly, not so much to actually fight.
Yes, Leah did something like that, but I'd say that's a mixture of glamour for the looks and unseelie magic for the defense.