For his defense special power, if I rolled a 1, how much damage would he ignore, 0 or 1? The way I see it, half of 1 is .5 and I would think for a half value you would round up. Am i correct, or wrong in this case? I want to be sure I am using him right. I just figured it worked like a conditional Invincible. I would also assume if you rolled a 3 you would ignore 2 damage and ignore 3 damage if rolling a 5.

You are correc. You always round up and as you are calculating how much to ignore a roll of 1 ignores 1 damage. A roll of 3 ignores 2 damage.

If you're wondering for exact wording from the rulebook

ROUNDING
At any point in the calculation of a value, if you have a
fractional value (usually caused by “halving” a value),
immediately round up to the nearest whole number