Let me do Tich's job right now.
forums.mtgsalvation.com/showthread.php?t...This link will show you a crapload of awesome red cards for multiplayer deck.
Single target cards such as Shock, Lightning Bolt, Lava Axe, etc.. will be less effective in multiplayer.
Allow me to suggest some cards I found in that guide I just linked.
Flame Rift 
Acidic Soil 
and of course
Earthquake 
Fault Line 
Glacial Chasm 
to save your ass from these final blows.
Seeing you will burn aggresively and that you have a lesser creature force to defend yourself with (considering you also want to attack), There are some cards that makes it less interesting for your opponent to attack you, with these in play, they might try to finish off another low life opponent (that you got low with your burns)
Fumiko the Lowblood 
Kazuul, Tyrant of the Cliffs 
I'm actually thinking of a control red deck where I want to discourage my opponents from attacking me.
Master Warcraft 
Rage Nimbus 
Aether Membrane 
Flayer of the Hatebound 
Wild Ricochet 
for some more control
Insurrection 
as a final blow
Sulfuric Vortex 
to make sure even the leading opponent won't be too high on life while I try to turn everyone against each other...
I know I'm pretty far from your deck theme now but I'm just throwing in some ideas..
