[Ickarium]

Spoiler for Tasuya & Blocking Magic:

Tatsuya was a 'Born-Specialized Magician'. They tend to be heavily, heavily specialized but able to do some extraordinary things others cannot. They can often use their abilities without a CAD, and if their ability is something reproducable with magic, can do that specific effect better than a 'general' magician. Tatsuya using his powers to break an activation sequence doesn't need a CAD. Teeechnically there are a few things that make it /better/ with a CAD though.

Spoiler for Antinite:

The books don't go into detail in how much Antinite is required. Antinite is re-usable. How it works is you pump psions into it and the antinite creates lots of meaningless psion waves in the area that make it very difficult to cast magic. I'm going to use a metaphor: think of it as a tuning fork that creates dissonant sound, the tuning fork is reusable. This lets even very weak magicians block powerful magic. As for how long, again they don't go into detail, but from the method it says they use, it should last as long as the person can pump psions into the antinite, so depends on the strength of the user.