A few Mechanic Questions

1. Does Metal Fist Mastery increase the damage of said skills by +50%, or multiply it by 1.5x?

2. Acceleration Bot EX-7 decreases monster def by 30% at max level.
2a. Does this translate to -30 PDR? If so, if the monster has only 10 PDR, will it decrease it to 0 or -20 PDR?
2b. Does it decrease an enemy's magic defense too?
2c. Does it work on bosses? How about non-mobile bosses such as Zakum?
2d. Does it stack with skills such as threaten?

3. Is it a bad idea to sacrifice mastering Metal Fist Mastery for Healing Robot H-LX? I was thinking about taking this route for future bosses with pot-cooldown.

Thanks in advance.

1. Does Metal Fist Mastery increase the damage of said skills by +50%, or multiply it by 1.5x?

2. Acceleration Bot EX-7 decreases monster def by 30% at max level.
2a. Does this translate to -30 PDR? If so, if the monster has only 10 PDR, will it decrease it to 0 or -20 PDR?
2b. Does it decrease an enemy's magic defense too?
2c. Does it work on bosses? How about non-mobile bosses such as Zakum?
2d. Does it stack with skills such as threaten?

3. Is it a bad idea to sacrifice mastering Metal Fist Mastery for Healing Robot H-LX? I was thinking about taking this route for future bosses with pot-cooldown.

Thanks in advance.

2c: It didn't make headless horseman move faster when i used it

3. There are 155 points for 3rd and you get 153. I'd rather drop 2 out of healbot.

2a. As far as I know, all skills that reduce monster def do it by the percentage listed, like it doesn't subtract it.
Reducing by 30% is more like .7*PDRate, (1-.3). So if a monster has 10% PDRate, it'd be 70% of 10% (-30% of 10%), which would be 7% PDRate