I am a theist, what do you think of my proof for God existing?

[Simon Moon]

This is my proof for God existing.

1. Formulate the information of the concept of God, thus:
"God in concept is first and foremost the creator and operator of the universe and man and everything with a beginning."

This is the fallacy of affirming the consequent. Strike one.

You are stating your conclusion, that a god exists, in  your first premise.

This fallacy follows the form:

1. If P, then Q
2. Q
3. Therefore P

Here is an example:

If I have the flu, then I have a sore throat.
I have a sore throat.
Therefore, I have the flu.

2. Look for instances of causation in reality outside of concepts in our mind.

3. We find countless examples of causation in reality outside of concepts in our mind.

This is the fallacy of composition. Strike 2.

Just because a part of something has a certain attribute, does not mean the entire thing does.

This fallacy follows the form:

A is part of B
A has property X
Therefore, B has property X.

An example is:

1. hydrogen is not wet
2. Oxygen is not wet
3. therefore water is not wet

4. From the countless instances of causation in reality, we infer to the existence of a first and ultimate cause.

This is the fallacy of equivocation. Strike 3.

The things we observe that you are referring to as 'countless instances of causation', are all instances of existing matter and energy, being acted on by natural forces. Ex material, as it were.

The universe according to you, is not previously existing matter and energy being acted on by your god. He is creating (causing the universe to come into existence) ex nihilo.  

You are equivocating the phrase 'countless instances of causation'. In one instance you are referring to creatio ex material. The next instance you are referring to creatio ex nihilo.

5. We find that the first and ultimate cause of all instances of causation in reality corresponds to our information on the concept of God, namely, the creator and operator of the universe and man and everything with a beginning.

This is a non sequitur. Strike 4.

This does not follow from the previous fallacious premises. Even if your previous premises were valid, it does not follow that the 'first cause' has to be a 'being'. All you are getting at is a first cause, which could be a materialistic first cause.

6. Conclusion: God exists in concept as first and foremost the creator and operator of the universe and man and everything with a beginning.

Does not follow from your syllogism. Every premise is flawed.

Your modus ponens is broken.