Both easy problems.
Temperature: You always need to build your string in the format "Label [value representation]". So it’s probably something like “Temperatura exterior [%.1f]” (untested, please post your result). It often helps to look at the events.log file to see what a variable is set to internally and then build the representation accordingly.
There is btw an transformation file out there you might find useful: Yahoo Weather - DE (German) translation file
Date format: This is a known problem and tells me, that you are not using the latest snapshot. The problem has been solved around two weeks ago.