The meaning of "affection upon" and affection for" are the essentially the same. The only difference is that "affection upon" is a much older usage of the English language. We now very commonly use "affection for" somebody or something in our day to day speaking and writing. I hope that helps!

You wouldn't say 'he beamed upon' these days. you could say 'he showered affection upon his friend' and then think about it as having an actual effect upon the friend. 'He beamed with affection for' speaks of the state of mind of 'He'. 'Beamed upon' perhaps speaks more of the effect on the friend.

"For" is the correct collocation for "affection." The only reason "upon" can be used in the example you gave is because "upon" goes with "beam." In other words, in "he beamed with affection upon his new friend," "affection" is being used in the sense of a ray of light, and "he" is "emitting" the affection (like the sun emits light upon, say, a flower) on his new friend. Otherwise, I would never say "I have a lot of affection upon you." You should say "I have a lot of affection FOR you." So think of "upon" as going with "beam," not with "affection."

I agree with Teacher_Greguk. However, there is a possibility that "upon his new friend" means the new friend is aware that he is beaming with affection, while "for his new friend" might indicate that the new friend is unaware that he is beaming with affection.