So I’m trying to understand what you are trying to do. (I don’t use any exchange rate stuff)
Tell me if this is the basic gist of it:
You have a date and you need to get the record where that date is in the range of effective dates for a table that only has effective from dates. Does that sound correct?
I think I would use this technique to get the specific record that I needed, and then if you need more than one, either duplicate the sub query for each field, or rejoin the table using the one field that you pulled. You can make your subquery joins be > and then return the top1 for that subquery.
Let me know if that makes sense.