Hi @Kenneth_Beck, you can track the points usage and manage your keys using our Developer Dashboard. If you click on “TopUp Account” in the dashboard, you’ll also be able to see a pricing table indicating how many points you can receive per USD spent. Entering a dollar amount in the box that appears will also show how many points would be purchased. You can take a look at our How to Make Efficient API Calls article for some tips on how to reduce point usage.
Regarding your second question, the PurpleAir API was designed and implemented before the Data Download Tool became available. It will always be fully supported to directly query the API instead of using the Download Tool.