The bracers cast the spell, not the person wearing them. They cast it at will so they can do it every round, round after round, all day long. Or not. It's up to the bracers.
I always understood the "Can cast x spell" to mean that a spell is chosen when the item is created and it only has that one spell forever. If you roll on that table more than once you could get more than one spell, of course, but each time you get just the one spell. That spell is built into the item just like the rest of its abilities.
As to your question about whether you did it right: No, I don't think so. Getting a cursed item is random (bad luck). Getting an intelligent item is a deliberate act by the person creating it; it doesn't just happen by accident.
That 1% chance rule is STRICTLY for when you randomly roll treasure for a random treasure hoard. You could, you know, NOT be running Rise of the Runelords and instead you could be making up your own adventure as you go. If you did that, you might just create some dungeon somewhere and put some monsters in it. Then you might wonder what treasure those monsters have, so you roll on the charts to figure out how much gold and magic they have. If, in the process of doing that, you decide to roll up a random magic item, then you might also roll the 1% chance that it is intelligent. This doesn't mean that whoever made it got a pleasant surprise when they accidentally made an intelligent item; it simply means that somewhere, some guy decided to make an intelligent item and it randomly ended up in the hands of the monster you put in your dungeon.
That's not to say you cannot roll the random chance every time a PC makes an item, but as you can see, it gets out of hand very quickly. These bracers are almost certainly way too powerful and way too expensive for a character of that level, and having them in game could create a lot of balance issues for you to deal with.
On the other hand, monks generally suck big time, so this added boost might keep the guy passably competent.