To go to meet (someone)

"Might as well" usually indicates that there's some reason not to do it, or that you're giving in to pressure, or that there's no better alternative. For example: She said she has been there many times, but really wants to go again. I don't see the point, but if she really wants to I suppose we might as well take her there again.

Both Steve and John omit the other possible meaning of "must have", which can also be used if you believe that, in spite of some small uncertainty, there's strong evidence that someone did it--so they "must have done it." For example: Dick: I think Sally must have eaten the last chocolate pudding from the fridge, don't you, Jane? Jane: She must have eaten it--just look at her mouth and hands! If you wish to indicate uncertainty you must use a questioning tone of voice whereas a level or emphatic tone, as when stating a fact, indicates you're quite sure (based on the evidence).

This means: “Sales of Taylor Electronics have increased substantially over the past year, which was a result that some analyst attributed to the CEO’s strong leadership”. Omission of "which was" in such sentences is common usage. And note Nanren888's comment about "analysts" instead of "analyst".

"in first grade" and "in third grade" mean the same as "in the first grade" and "in the third grade" and are probably more common usage; otherwise, the sentences are fine as is. I'm not quite sure what you're asking about with the three choices "I, we, you", but if you mean substituting "I" for either "We" or "You" in the given sentences, neither would be good usage.

"...but the colors would dim" means the memory would not be so clear, being dulled from the alcohol. "Beckett stopped at the bottom step" means that Beckett had been following her but (when they reached a stair) he stopped at the bottom step and didn't follow her up the stairs. "he tried and failed to keep his eyes off the place her hands joined her arms" means he was unable to keep looking at the place her hands joined her arms (presumably, her wrists, though I'd need more context to be sure).

"...but the colors would dim" means the memory would not be so clear, being dulled from the alcohol. "Beckett stopped at the bottom step" means that Beckett had been following her but (when they reached a stair) he stopped at the bottom step and didn't follow her up the stairs.

If you intend to express surprise the expression is "What the f**k!" and for confusion or similar "What the f**k?" So the only difference is the punctuation (or intonation if voicing it). "What a f**k!" would express great satisfaction after intercourse, but "What a f**k?" is just incorrect in general, though street slang might well use that form, as well as "What da f**k?" or even "Wha da f**k?"--all just slurred pronunciation of "What the f**k?"