The phrase "went to him" implies that you went one time; you checked, and you went - both actions were completed. The phrase "going to him" can imply an ongoing situation, such as going regularly to a doctor. The second construction can mean either you went once, and done - or more than once (an on-going situation).

Yes, it is correct, when you really want to emphasize a specific person doing an action. You can say "he is sending candy and you are sending flowers", no emphasis on either action. To emphasize the importance of the fact that you are responsible for the flowers, (for example, if the flowers were discussed before, and you are now re-stating the agreement) you say "he will send the candy and you, yourself, will send the flowers. This usage is called "emphatic usage of the reflexive pronoun"

To antagonize is to make else someone feel hostile. It is an effort to provoke someone to feel angry. You can antagonize someone, but you cannot antagonize yourself. You can be antagonistic, which means you are behaving in a way designed to make someone feel antagonized. As in "you've behaving so badly! Stop being so antagonistic!" Or, "I told you to stop antagonizing your brother!"

It is still used, but probably more likely with people in their 40's and above.

He would take his houseboat from the land to the lake or the river. Thats what is meant by "go out in the houseboat". According to this sentence, he made the houseboat, took it out on the water, and then painted scenes that he saw while he was on the houseboat.

Get in the way of means "to prevent" or "to delay" someone doing something. An example would be "don't let your new hobby get in the way of completing your studies". It refers to the fact that a person has a choice between two or more things, and must be careful not to let one choice prevent them from doing another thing.

You would say "in a video". The only time you would omit the "a" is if you changed the sentence to "i have proof in video form" but that is quite unlikely to be used.

Essentially the both mean the same thing; to be annoyed is to be slightly angry. It is an emotional feeling that one has. You can be annoyed, and someone can be annoying to you. Irritated, however, can mean not only an emotional feeling, but it can also be physical. You can say “his skin was red and irritated”. It can involve an aspect of the body, as in “his eyes showed slight irritation”. Annoyed cannot be used in this way, it is strictly for emotion.