Forget trying to figure out the nitrites and nitrates yet. They aren't going to matter until your ammonia reading reaches 0. As for a chart that will give you the nitrate from a nitrite test, throw it in the trash and get a nitrate test. As the ammonia goes to 0, the nitrites will start up and then come back down to a 0 reading. While it is coming down, you will see the nitrates start going up.
Nitrite readings have nothing to do with nitrate levels. Nitrate can be at 1000ppm and the nitrite reading can be 0 at the same time. Vice versa as well.
http://faq.thekrib.com/begin-cycling.html
Has a chart that shows you what happens with ammonia, nitrite and nitrate levels.
At 7 1/2 weeks, yes, it is still going through its cycle.