This lyric refers to the rapper commuting to conduct activities in his territory of choice, in this case being Saint Clair Avenue in the city of Cleveland.
A "fifth" refers 1/5 of a gallon of liquor. Fifths along with pints and half gallons are sold at most liquor stores. Taking something to the dome (or head) refers to using it all yourself. He drinks a fifth himself.
selling substances that look like drugs but aren't, as a desperate measure to make money. this is dangerous, because you can only fool people so many times until you get a bad reputation on the street that your product is fake and people want to hurt you.
this means you are wondering if you're ever going to succeed in life or reach some level of accomplishment, like when you are heating water and it takes a long time for it to finally reach the boiling point and bubbles finally appear
i manage my drug dealing business very well - i'm careful with my money, and don't allow anyone to steal it or buy drugs from me at a discounted price. im never short money when it comes time to pay my supplier or buy more product, so i never lose money.