lethal damage to everyone, who wins? what if lifelink?

ive hit a snag with my deckbuilding

its an activated-ability based deck using [[mairsil, the pretender]]

my finishers for the deck were going to be cards like [[crypt rats]] or [[pestilence demon]]

they have other synergies in the deck hence why I chose them as a double whammy

my plan way to make infinite mana, activate these for 999, and win.

however, after actually properly reading the cards, they are not assymetric atall, meaning they hit me in the face just as much as they hit everyone else.

so a few questions:

- if I activate crypt rats for 999, (lets say Im at 1 health, player 2 at 2 health, p3 at 3 health, and p4 at 4 health), do we all die at the same time? does it tick up and I lose and p4 wins? how does it work?

- if I repeated the first example, but gave crypt rats life link instead, would it be any different?

- if I repeated the first example, but gave crypt rats infect instead, would it be any different?