The Greek word translated as "then" means "but", "however", and "on the other hand". Since it always falls in the second position, translating it as "however" often captures its feeling better. 

"Said" is from the Greek verb that means "to say" and "to speak" also.

The word translated as "the lord" is the same word that is often translated as "Lord" or "the Lord" in the NT. It also means "lord", "master of the house," and "head of the family." It is the specific terms for the master of slaves or servants, but it was a common term of respect both for those in authority and who were honored. It was the term people used to address Christ, even though he had no formal authority. Today, we would say "boss" or "chief".

"Of the vineyard" is from the genitive form of the noun that means simply "vineyard."

The word translated as "what" means primarily "anything" or "anyone," but Jesus often uses it to start a question so it means "who", "what", or even "why". 

The Greek word translated as "shall I do" has the primary meaning of "making" or producing" something or "causing" or "performing" as service. It describes a productive action.  It is not as broad a word as the English "do", which covers all actions, productive or not.  The form of the word is more likely that of possibility than the future tense.

"I will send " is from a Greek verb that means "send", "send forth", "send away", "conduct," and "escort." The form again could be the future but it is more likely that of possibility.

"My" is the regular first-person pronoun in Greek in the possessive form, so "my" or "of me".

"Beloved" is an uncommon adjective for Jesus to use that means which means "that with one must be content" when specifically applied to only children, "to be acquiesced in" (the choice of least evils, "one must be content", "desirable" (of things), and "beloved" (of people). It is an adjective form of one of the words the NT translates as "love" but it has the sense of welcome. We only see this word here and in the parallel in Mark.  This word follows "son" and is preceded by its own article so that either it or the following word (see below) are treated as a noun.

The word translated as "son" more generally means "child" or "children". It can refer to all offspring in later generations, just like "father" refers to all previous generations. Jesus also used it metaphorically to describe those who follow a way of thought or set of beliefs that descend from an individual. More about it in this article.

"It may be" is another uncommon adjective that means "equal" in size, strength, number, or rights; of persons, "fair," "impartial"; of ground, "even," "flat"; generally, "just", "fair." It is also used to mean an "equal share" or "equally distributed." It is not a verb. It could act as a noun because of the article before "beloved". The phrase that makes the most sense is "the beloved equal".

 The word translated as "they will reverence  " primarily means to "turn around." In the passive used here, it has a sense of feeling misgivings about what you are doing. It also means to respect or reverence, but with a sense of changing behavior.

 "Him" is a demonstrative pronoun that means "this one", "here", "the nearer," and "the familiar."

There is no "when" in the Greek.

There is no "they see" in today's Greek but there was in the source that the KJV translators used. 

 There is no "him" in the Greek.