Breaking down a simple sentence

Breaking down a simple sentence
 

If we use this statement as an example:

Él se lo dice a Juan.
He tells it to Juan.

El / he
se / him, her, them, you plural
lo / it
dice / he, she, you in the formal tells
a / to
Juan

So if we translate the above literally we would get,,,
He, to him, it, he tells, to Juan

I can not understand why we must use "se"
Is it incorrect to say...
El lo dice a Juan

Is this another option?
Él dicirlo a Juan.
or should it be...
Él dicirselo a Juan.

Any help would be greatly appreciated!
Oh, and sorry for the lack of punctuation.

The indirect object pronoun 'se' takes the place of 'le', which is the usual third-person singular pronoun, or 'les', the usual third-person plural pronoun. This happens whenever there is also a third-person direct object pronoun prior to the verb. The Spanish don't like the cacophony of 'le lo', or 'les lo', so the indirect object pronoun is changed to 'se'.

The indirect object pronoun 'le' ('se' in your example because of the reason given above) is ambiguous. It can mean any singular third person. In order to clarify which third person was meant, we add the indirect object - 'a Juan'. The indirect object will always be preceded by the preposition 'a'.

Both the third-person indirect object pronoun and the indirect object are specified, even though the indirect object, whose purpose is to clarify, makes the pronoun redundant. It isn't always necessary to use both the indirect object pronoun and the indirect object. If the object is known, there's no reason to clarify, but the pronoun must be used.
It's possible to not use the indirect object pronoun when the indirect object is provided. For example:
Escribo a Marta. (I'm writing to Martha.)
But, it's perfectly good Spanish to include the pronoun:
Le escribo a Marta. (I'm writing to Martha.)

Let's add a direct object to the mix.
Escribo una carta a Marta. (I'm writing a letter to Martha.)

Note that no pronoun was used above. Of course, it's possible to add the indirect object pronoun with no change in meaning.
Le escribo una carta a Marta. (I'm writing a letter to Martha.)
And, if the indirect object is known, it's possible to drop it (but keep the pronoun).
Le escribo una carta. (I'm writing a letter to her (Martha).)

However, when the direct object 'carta' is referenced with a pronoun (the feminine 'la'), both the indirect and the direct object pronouns must be present to avoid the confusion that may arise because of some dialectual usages. And, as stated before, the indirect object pronoun 'le' is changed to 'se' to avoid cacophony.
Se la escribo a Marta. (I'm writing it to Martha.)
Se la escribo. (I'm writing it to her (Martha).)

Using this information, your original sentence should now make sense.
Él se lo dice a Juan. (He tells it to Juan.)
If the indirect object (Juan) is known, it can be dropped, but not the pronouns.
Él se lo dice. (He tells it to him (Juan).)

This is not a cut-and-dried issue in Spanish grammar. It is not necessarily wrong to say "él lo dice a Juan", but it is much more common (and often expected) that one says "él se lo dice a Juan".

This type of pronoun doubling is extremely common for third-person indirect objects. Normally the clarifying phrase ("a Juan" in your sentence) is stated only once, and afterward only the pronoun (se/le or se/les) is used afterward, unless there is a need to show emphasis or contrast.

No: an infinitive cannot serve as the main verb of a complete sentence.

I agree. I am thinking that in a religious context "se" is often omitted:

"Jesús lo dijo a sus apóstoles" instead of "Jesús se lo dijo a sus apóstoles". The first sentence sounds more solemn, higher.

One particular issue that comes up regarding "lo doy a Juan" and "se lo doy a Juan" is that "a Juan" itself is ambiguous: depending on context, it may be either a direct object marked by "personal a" (a definite direct object that identifies a person must almost always follow the preposition 'a', while a direct object that identifies a thing does not), or it may be an indirect object (all indirect objects are introduced by a preposition, almost always 'a').

So, in the sentence "lo doy a Juan", it is not necessarily clear whether I am giving Juan to someone else or whether I am giving something to Juan. It's true that most of the time it is reasonable to assume one or the other interpretation. However, most native speakers conventionally and automatically say "se lo doy a Juan" in order to more clearly eliminate the possibility of thinking that "a Juan" is a direct object.

Wow! Thank you all so much for your time and input. Do I understand it yet? Nope, not so much...BUT...I will read and reread every one of your posts until it sinks in.

Ughh....it would have been so much easier if everything I said was correct. :)

Thanks again for all of your help!

OK! After going over this with clear head, it is making sense.
I find it pretty incredible that you folks are willing to spend the time to help a perfect stranger.
Much appreciated!

Good to know you're finding the forums useful.
We're all here to learn and to help learning. ;)