while you're spending time with a lady, if she ever acts as if you are a couple (says "let's go back to our house" or "let's get in our car" etc.), things have gone too far and you must get rid of her before she wants a serious relationship or your money.
this is a reference to children in some foreign countries being recruited and trained in the military well before the age of 18. here they are being rewarded with a soccer ball for killing 5 people in the enemy's army
while the explanation about cocaine is accurate about that drug, i think he is actually high from smoking marijuana and is comparing this high to the fact that nose bleeds sometimes occur at high altitudes because of dry air
rather than treating a female to a nice dinner, Eminem is saying he will only give a woman one slice of pizza and a can of Faygo soda pop (a brand of soda common in the mid-west) - this is also an insult to the rap group ICP who often talk about Faygo