Where can I see how much each vendor earned and how much commission I kept?

Go to Vendors → Vendor Earnings.

1. Click Sync from orders to bring in the latest orders.
2. Set the From and To dates and click Apply. Click Reset to clear them.

The By vendor table shows each vendor's Orders, Order amount, Admin (your commission), Vendor earning and Unpaid.

Below that, each order line shows the commission Rate and a Status of Unpaid, Initiated or Paid. You can filter by vendor and status. Once you have paid a vendor outside Wcart, click Mark paid on those lines. Click Unpaid to undo it.