This is a discussion on How long to level up? within the online poker forums, in the Tournament Poker section; TLDR:
It will take me 9 weeks of playing 7 hours a week to bump up to the next level.
Is my math sound?
There are some parts of the math that I am not sure what you are doing so I will not comment on the math but will comment on your overall take which I think is wrong. You are trying to figure out how long it will take to have the roll to move up but right now you are a losing player (counting the rake of course). Meaning that if you play at the same win rate you are playing now more hours will lower your bankroll not increase it. You will need to get your win rate up to be able to move up. As I took what you wrote, you are under the assumption that you could play for 9 weeks and be at a higher bankroll. How could this be if your win rate doesnt change and every 70 tourneys you play you are negative?
My advice would be to work on your game and work on getting the win rate up so you are positive per tournament over the long run including the rake. Then you can do the math based on your win rate per tournament to see how much you need to play to have the bankroll to move up.
21 cents of rake for a $1.50 seems high to me but I do not normally play sit n gos so that may be the norm. I would see if the rake on 45 man SnGs is also the same rate of rake as these are or if they are lower. You are showing so far that you can beat the game but you cant beat the rake. You probably also need a bigger sample size then 70 to know your real win rate but I also don't think you need a thousand either. Continue to keep track of things but before thinking of moving up you need to be beating the game and rake you are currently playing.