How is the "additional damage" from Chosen weaknesses calculated?

Question

Some of the Chosens' possible weaknesses make them take additional damage from particular damage sources. These are:

• Shell-shocked - additional damage from explosives.
• Brittle - additional damage from close range attacks.
• Bewildered - additional damage when attacked 3+ times in a single turn.

How is this 'additional damage' calculated? Is it proportional to the damage of the attack in question, or is it a static bonus?

Answer 1

According to this page, it's a mixture of flat bonuses and multipliers.

• All of the faction weaknesses are 50% more damage, rounded down.
• Bewildered is a flat 3 extra damage starting on the third attack.
• Shell-shocked is double damage from explosives.
• Brittle is 50% more damage from within 4 tiles.

I haven't personally confirmed these through experiment, but they seem to match by experiences. Nothing in here seems "off" to me.

The full page goes into much more details, including some edge cases, e.g. adversary: Reapers will increase claymore damage regardless of who blows it up, but will not increase remote start damage.