I'm loving the widget part but found few errors:
1. For some reason I have to use a VPN or else it doesn't load for me (perhaps it has to do with the server's location).
2. Whenever I choose a different currency for the rates (middle option for the widget), the exchange options (last one) also changes. Why?
Item 2, not all exchanges carry all currency pairs. Because of this, the list of exchanges has to be reset each time you change either the source currency or destination currency. I'll see about adding in an option to keep the same exchange if it is still valid after you change the currency, but as it doesn't keep the program from working it won't be a high priority.
I know it has been a long time, but I wanted to circle back on the currency change. After reworking how the currencies are selected in the dropdowns, your issue with the reset has been fixed. When you change the 1st currency the 2nd currency will be kept at its current value if there is an exchange rate available between the two currencies.