You've got the bulk of it.
Track rake independently as well as a part of your gross debits - you'll eventually want to look at the ROI variation based on rake at specific limits (as an example, I play cash rather than SnG's, but the rake at 10nl and 25nl is a killer percentage of your winrate compared to the rake at 50nl and 100nl, I'm sure this applies to the SnG fees as well).
Track bonuses/rakeback as part of your gross credits and independently. You'll want to be able to track ROI based strictly on your play, but will want to be able to view gross ROI as well. "Rakeback Pros"/"Bonus Whores" make a significant percentage of their profits based on rb/bonuses (I'm not knocking the practice) but still want to be able to see their unadjusted winrate.
I suggest that you simply treat your deposit as your initial br - hopefully this will grow over time, and with proper br management and game study, your br should grow over time - so hopefully it's a one time thing (it wasn't for me ). But don't treat it as something you can withdraw until it grows big enough to treat that way. That's not to say you can't withdraw it, just that it's not healthy to view it as something you will withdraw until it exceeds your br requirements.
So, let's say we're playing 5nl, and want to maintain at least 20 buyins (sorry for the cash game example, I'm not familiar w br logic for SnG's) and never plan on playing a higher limit, I might plan on withdrawing $50 when my br grows to say $175 (i.e., withdraw 10 buy ins when I've got 35 buy ins, maintaining a minimum 20 buy ins plus a 5 bi cushion). Note, though, that if I plan on playing a higher limit, I won't want to touch the br until it exceeds the minimum to play the limit I want to play at.
If you use a spreadsheet instead of WordPad (MS Works includes one, forget what it's called, you can also google free spreadsheet tools, Sun distributes one, forget what it's called), you'll be able to calculate and graph more quickly.
If you feel like it, try downloading the free trial version of either PT3 or HEM and look at the tabs under Tournament play, and the graphs, to see what financial stats are usually tracked.