A Milli

Tha Carter III Lil Wayne
venereal disease refers to the fact that his lyrics are "sick". See my other explanation for the second half.
The line is "like a menstrual I bleed through the pencil and leak on the sheet in the tablet of my mind" and is a metaphor for writing lyrics in his head,compared to the female menstrual cycle.It also sounds like "minstrel" which was a medieval songwriter
Lil Wayne is referring to taking a hit of Marijuana smoke that is so thick and void of oxygen it is like breathing in higher altitudes where the air is so thin you feel like you are choking.
in the pen sharing showers means in jail because prison is often referred to as a pen and they have communal showers.
Bic is a lighter company, so he keeps that heat or gun on him
The things he has done in his career is more than you have done in your career, so it isn't fair
Some rappers either refer to themselves or act like goons but Wayne infers that he's a goblin which is better/greater/cooler than a goon so what are you going to do about it
Bic references the cigarette lighter brand, and "keep that flame" means he smokes pot for prolonged periods of time
we will be known for firing our guns and killing people (it will make a popping noise that is just as recognizable and commonplace as Orville Redenbacher's popcorn popping)
Basically, this shows the imagry of his car crossing a bridge, while be very conspicuous and noticeable, as if it were dancing.