The idea is to get yourself in a position where it is easy to prove that you did not improperly charge GST on your invoices or claim ITC's from costs prior to obtaining the tax number. It's great that you have a spreadsheet to explain the circumstances.
You will need to report all of your income on the GST34, so the amount of GST collected in relation to the income may appear low. The input tax credits may appear low as well in relation to the income. I don't anticipate this being a problem, but you never know. Do not add GST to any of the income in the sales section of your tax return, as it is reported and remitted on the GST34.
If you are a quarterly filer, you could file Nil returns for the first two quarters of the year, and then report appropriately for the next two quarters, but if you are an annual filer, just report on the year end report.
It sounds like you are in pretty good shape.
