Does EMS charge count towards Mosaic Challenge?
 

I'm about $150 short of the the required base fare to complete my Mosaic challenge. If I pay for EMS seats, does the upgrade fee count towards the base fare points to qualify for the challenge?

I don't think so as it doesn't credit as "base points" to the program. Call and see if they can up-fare to a higher fare class, maybe?

speaking of....looking at a fare and "Blue" is $330, "Blue Plus" is $345 and "Blue Flex" is $430.

if i buy the Blue Flex, how much of that converts to mosaic points?

Approximately 88-90%, assuming a domestic flight. When choosing the fare scroll down on the webpage and you should see a breakdown for "fare" and "taxes & fees" before you click continue. The "fare" part there should all count AFAIK.