Yo

So, it says that "each monster within 3 spaces of you recieves -1 heart on all attack rolls."

Does that apply to all rolls made, even those who are not intended for Leoric?

Yes.

Leoric helps all his friends nearby.

Leoric is a good man then

I have a question about Leoric ability. It says " each monster within 3 spaces of you recieves -1 heart on all attack rolls. (to a minimum of 1) ". Does it happen before you apply surge or after?
For example: my red spider make roll with 1 heart and 2 surges. Is it eventually does 3 damage ((1 for heart - 1 for Leoric) to a minimum of 1, and then using 1 surge for +2 hearts) and inflict a poison? or it does only 2 damage (1 for heart, 2 for surge and -1 for Leoric)?

Leoric's Hero ability is applied after dice are rolled but still in step 2 of the attack. That is before any modifications from surge abilities are applied to the attack result in step 3.