Your comments

You can click "report" on any of those sales that are incorrect.  That then queues the sale for review by moderators and admin.

This should be fixed now.  Please confirm that you can see that drop down for price increase and price decrease.

You can sort by price change in your collection but it is based on the recent price change in the value, not in the value since you added it to your collection.  There should be a "price change" option in the sort drop down on the page.

It is on our roadmap to add in January.  Hopefully it will be live on the site soon.

The grades are a number grade that a 3rd party company has given the card based on it's condition.  Companies like CGC, PSA, and Beckett are the main grading companies.