VexingQuestions' Deotic-Ontological Argument

VexingQuestions' Deontic-Ontological Argument (DOA) is one of the oddest arguments I've seen for the existence of a perfect being. It is presented as follows.

1. I ought to attain the highest form of happiness.
2. I ought to attain the highest form of happiness only if is possible that I attain the highest form of happiness.
3. ‘I attain the highest form of happiness’ is identical to ‘there is a perfect being and I am in communion with it’.
4. If it is possible that there is a perfect being and I am in communion with it, then it is possible that there is a perfect being, and it is possible that I am in communion with it.
5. A perfect being is identical to a necessarily existing maximally excellent being.
6. Therefore, a perfect being exists

Premise one doesn't seem very obvious. Even if there is a highest form of happiness, I don't see a very strong reason to say that I ought to attain it. 

I'll grant premise two. However, with these two premises, I believe the first premise should state "I ought to attain the highest attainable form of happiness". 

I don't see a reason to accept premise three. There can be a "highest form of happiness" without a God existing. It would simply be the highest form of happiness that you can attain without God. I can't say exactly what this is, but I'm sure it's out there. 

The highest attainable happiness, is attainable. Even if an advocate of this argument does manage to demonstrate that the third premise is true, the atheist can simply reject the first premise without a problem. To say you don't ought to achieve the highest form of happiness is not problematic if that happiness isn't attainable. Thus, I believe my replacement of the first premise is much better, because it doesn't assume that the "'actual' highest form of happiness" can be acquired. 

Furthermore,I would think that some people would want different things, and things that make some people happy wouldn't be the same for others. For instance, some people wouldn't take pleasure in worshiping a genocidal (see Noah's Flood), egotistical (see first four of the Ten Commandments) tyrant (see Hell), while others would (Note: I'm not attacking the morality of God, I'm simply stating attributes that can be ascribed to him).

I'll grant premise four.

While premise five is intuitive, I don't think that there is a strong reason to accept it, as it seems to be implying logical necessity is a perfection.