Is skill like ice can't affecting the card itself only or all cards that it is attacking with ?

You have to have at least one matching card played, and all others used at the same time benefit from the awakened skill. Multiple skill awakenings are possible for added effect!

So will 2 ice fang stacks itself? From 2 different cards

To my knowledge, yes. If you have three immortals each with ice fang, then you should get ice fang effect x2. (total minus one for triggering the awakening)

On a similar subject. When a skill triggers, it give a one time bonus for all cards being used on that 1 attack, right?

Also, are assist bonus' and penalties one time or full battle? (IE if my attack is 10k and someone assists adding 1k attack, is my attack 11k for the next attack or until the battle ends?)

I cannot confirm that. There's many factors to consider (assists, attack combos, elemental bonus and awakenings)