Welcome to Tiller, @matt_harrison. Sounds like you’ve come a long way.
If you’re looking for perfection, the Amazon offsets are a little bit crude as I documented here. The data from Amazon is imperfect so the approach is best-effort. The offsets should get you pretty close if you categorize the credit card transactions to Amazon as “Transfer” then allow the newly-inserted Amazon Offsets to zero those out (approximately) leaving on the new line-items as the long-term, go-forward expenses.
It’s ok to remove that cell-protection on the header (to run filters), but just be careful about typing over the header names as that can (appear to) break dashboards. (If you’re saying you can’t filter after overriding the cell protection, I’m not sure why that would be.)