Unless it says DICEPOOl then the bonus apply to each individual weapon?

If I have 4 limbs and I get a +1 Parry bonus then I get 4 parries and each one has a +1D6 - Unless it says dicePOOL right?

It kinda impacts pretty well if Ihave charging attack, knife specialization and have a dicepool of 12.

Skill 6 (+2) Knives
Attribute: 6

Dicepool 12/6= 2+ Spec 2 + Advantage 1= 4D6 X6 arms.

You can only ever roll one parry test per attack received - splitting a melee dice pool only applies to attacking with two (or more) weapons at once. You get a +1 bonus for using two weapons to parry, but it's GM's call as to whether more weapons would give a higher bonus. I think I would allow +1 per extra weapon - hitting a guy with six swords in your face should not be easy and +5 seems fair enough.

You always split the pool before applying modifiers unless it explicitly says otherwise (such as that one Multi-Attack Manuever thing). The MA qualities are modifiers. So you split the pool, then apply the modifier ie you are doing it right.

Aerospider is right that you can only ever parry once.

Can Styles for different martial arts be combined?

kickboxing - +1DV for unarmed attacks (X2)
karate - +1DV for unarmed attacks

Could I combine those and get a +3DV when making an unarmed attack?

Yes... to a maximum of +3 DV (it is capped at +3)...

all other bonuses however are not capped. Only the DV has a maximum increase.

The OP actually left me speechless. No, you don't get a 4d6 times 6, Christ.

This is True... Sorry if I did not include such. I did not mean to mislead.