Fallout 3 "The Waters of Life" Mission HELP!!?

Im at the part where u get in the tunnel to get to the citadel. that one guy is sick and i left him because I have no supplies whatsoever and limited life (enclave soldiers kill me in about 2-3 direct hits). Now the problem is getting out of here.Almost all my weapons ran out of ammo or need to be repaired( I KNOW perfect timing right?). All i have is the assault rifle with one full mag, and pistols that deal 4-8 damage. HELP