I'm sorry your dad is on that kind of mission. What a sad place to be.

Unfortunately, his information is almost completely inaccurate. Some of it is right, so that's good. :)

There's a lot here so I'll keep it as succinct as possible.

(1) God is never called "Jehovah" in the Bible. That word is completely made up. Why? Jews refuse to pronounce God's covenantal name, YHWH (or with vowels, Yahweh) because of several Old Testament texts. Instead of saying that word, they actually pronounce the word "Adonai" (which means, "My Lord"). So, when you join the  consonants of YWHW with the  vowels of Adonai, you get "Yawohaiw." Around 1100 AD the Y was changed to a J and the spelling was corrupted a little bit to "Jehovah." So, the actual name, Jehovah, is made up from two Hebrew words in an attempt not to profane the actual name of Yahweh.

Unfortunately, this means that what your dad stated is clearly mistaken (or whomever told him that information). It is impossible for Jehovah for be a son of El because the name "Jehovah" is made up. On top of that, it was made up about  3500 years after the Canaanite religion. And if your dad meant that  Yahweh was a son of El, that's also mistaken. The name of Yahweh didn't exist until the Jews introduced the term after it was revealed to them, much later than Canaanite religion.

(2) The term, "El" is a very old Canaanite/Semitic term. It means "deity or god." In various ancient literature it can be used as a general term for "god" or as a name for a particular god, the chief god of Canaanite religion. When it's used of one particular god, El, it refers to the Father/Creator of humans and animals in Canaanite religions.

In the Bible, the term "el" is used of other "gods" and it's also used for the God of the Jews. This is key: when they used "El" for the Jewish God, they didn't think that He was the same god of Canaanite religion. The Old Testament makes this very clear (there are numerous crucial distinctions like the fact that El in Canaanite religion had a wife named Asherah, while the Jewish God had no such relationships, and many more such big differences). Around 1500 BC or so, Jews were convinced that God/El revealed Himself in a particular, definitive way to Moses on Mt. Sinai in the burning bush event. At that event, they learn that God's particular name is "YHWH or Yahweh." Read Exodus 6:2-3.

So, your dad is right in that the God of the Bible is a few times called El Elyon, "God on High" (Gen 14:18-20; Deut 32:8; Ps 78:35;). In fact, there are about fifteen different forms of His name given in the Bible. They are just various titles for Him (like "God of the Mountain" and "The Righteous One" and whatnot).

Jews believed that His covenantal name - the one revealed to Moses -- was Yahweh.

All of this is quite irrelevant to the claims of Christianity. We don't worship a name of God; we worship God the Father through His Son, Jesus Christ in the enabling of the Spirit. Jesus is the center of Christianity, not a Hebrew name for God used 4000 years ago. Christianity rises and falls on the truth claims of Christianity: who Jesus was and is, what He taught and did, why He died, His resurrection, and His work in people today.

Well, that's all for now. :)

Keep up the good work! It takes time and patience sister!