The first assession about the victory point is AFAIK false, but it is true that in 1944-1945 German fighters were often sent chasing artilley spotting AC rather than Allied fighter-bombers.
The second story may be found at many places on the Internet, but according to this webpage (
http://forum.axishistory.com/viewtopic.php?f=71&t=1282) is coming from the book "The last battle" by Cornelius Ryan. While I like Ryan's book, AFAIK they are more based on personal stories than on official documents. That may explain why in all Internet sites I have found, the precise unit of the involved L-4 is not given, and neither is the date of the event. I will say that if it happens, there should be an official report somewhere.
But by the way, even if it happens, the last dogfight of WWII in Europe very probably happens on the Eastern Front. Soviet pilots reported meeting in the air German aircraft as far as 10 or 11 May.