John is told - come and see.
"And see" is an addition. The "come" is in principle the same as in V.3,5,7.
According to the UBS NT Graece (4th ed.), the certainty in that place is of category C, i.e. there is "considerable" (though not "very high") degree of doubt. But note that you argue with the lesser plausible variant reading.
One of the four beasts wants him to go to a place and see what is happening there.
A better translation would be "the first creature". (BTW: "beast" should be avoided, because literally it is a "living" [one] here, and there is quite another Greek word translated as "beast", in Rev 13 etc.).
Compare the phrase "the first seal", which is the same construction and
could be translated "one of the seals".
a rider on a horse
white -
Like a Roman general, when he is sent out to war. A "crown" could be given to a victor, too, so this word denotes here the ornament which stresses he is sent out to win the war. Unlike
diadem, the Greek word
stephanos is not limited to monarchical emblems.
I don't understand why some English versions say "conquer" when the word used clearly denotes a victory (Rev 6:2 is the only verse it is rendered as "conquer" in the KJV, 24 times "overcome", also "prevail" and "get the victory", one instance each).
Unlike your interpretation, which speaks of wisdom not mentioned in the text, my explanation is backed up by the text.