What is said in Greek is very different than the KJV translation. However, in terms of tradition, the statement about fasting is very odd in the Greek and the KJV tries to "correct" it.

"I fast" is the Greek word that means "abstain".

"Twice" is from an adverb that means "twice" or "double". The most likely sense is here is "double".

There is no "in" here. The noun is in a possessive form, which, when used with a time means "during".

The Greek doesn't say "the week". It says "the Sabbath" but the term "sabbath" was used to refer to the days between Sabbaths. However, this form is the masculine singular, which usually refers to the Sabbath day. The days of the week between Sabbaths is usually used female and plural form. The statement is odd if it refers to the Sabbath day because except on Yon Kippur, fasting was not performed on the Sabbath among Jews. If a Jewish fast day falls on the Sabbath, fasting is delayed until the following day, Sunday. However, this could refer to the Yom Kippur fast, which usually lasts for 25 hours but which this Pharisee may have extended to 50-hours.

A made-up word is translated as "I give tithes" It appears only in the Gospels and an uncommon one for Christ. It reverses the meaning of the normal word that means "to take a tenth" by adding the word "from" to it as a prefix. The sense is, "I take a tenth from [myself]."

The word translated as "of all" is the Greek adjective meaning "all", "the whole", "every," and similar ideas. In the plural neutral, the sense is "all things" or "everything".

The word translated as "that" means "as great as", "as much as," and similar ideas of comparison.

The verb translated as "I possess" means "to acquire," but specifically for yourself. It also means "to possess" in the sense of having something stored in opposition to Greek word translated as "to have" or "to hold", which means having it in hand. Since a tenth was unlikely to be paid on all stored items, the likely sense is about those things acquired.