Help with currency conversion using LOOKUPVALUE with Exchange Rate month by month

Hey Everyone, 

I hope that anyone can help me with a problem I have when trying to lookup an exchange rate for a transaction on a given month. 

I am using an Exchange Rate table as follows:

And I am using a Calculated Coloumn like this:

REVENUE_FORECAST_CURRENCYRATETO_USD = 
LOOKUPVALUE (
    'IFS_Currency_Convert'[CONVERSION RATE],
    'IFS_Currency_Convert'[FROM CURRENCY], Revenue_Forecast[Currency],
    'IFS_Currency_Convert'[TO CURRENCY], "USD",
    'IFS_Currency_Convert'[RATE DATE].[Year], Revenue_Forecast[PROJ_CREATED_DATE].[Year],
    'IFS_Currency_Convert'[RATE DATE].[MonthNo], Revenue_Forecast[PROJ_CREATED_DATE].[MonthNo]
)

But the results I am getting look like this:

As you can see the table to the left, are the transactions with the attempt to pull the currency rate, and the table to the right is a view of the currency table. You will see on many of the results in the transactions, it is doing some kind of sum for the exhange rate? Why is this? What am I doing wrong?

Additionally, and annoyingly, the Exchange Rate table that is used by my company does not include the rates used for same currency (e.g. USD to USD = 1 and GBP to GBP = 1). How can I easily add these exchange rates into the table on a Month by Month basis?