I think you are looking at this from an evolutionary point of view? Then it makes sense to make statements like "more and more complex states are less likely" (i.e., they take more time) and "intelligence increases with the complexity" (of organisms).
Outside this context, though, I have trouble understanding what is meant by "complicated" or why "more intelligent" should be more complex. In fact, you could skip right from (1) to (3) -- most theists would be comfortable asserting that God is maximally complex. However, is response to (1) they might counter with -- if something does exist, you can't use its improbability to negate that it exists.
I'm not sure most theists would be comfortable asserting that God is maximally complex.
The wikipedia article Complexity looks helpful.
It is true that if something does exist you can't use its improbability to negate its existence. But this option is allowed for in the argument; "unless there is other evidence or it has other properties that make its existence maximally more likely". So if God is, say, necessary, then he is going to exist no matter his likelihood. What this argument does is set a really low prior for the probability that God
I've often had half-finished LW post ideas and crossed them off for a number of reasons, mostly they were too rough or undeveloped and I didn't feel expert enough. Other people might worry their post would be judged harshly, or feel overwhelmed, or worried about topicality, or they just want some community input before adding it.
So: this is a special sort of open thread. Please post your unfinished ideas and sketches for LW posts here as comments, if you would like constructive critique, assistance and checking from people with more expertise, etc. Just pile them in without worrying too much. Ideas can be as short as a single sentence or as long as a finished post. Both subject and presentation are on topic in replies. Bad ideas should be mined for whatever good can be found in them. Good ideas should be poked with challenges to make them stronger. No being nasty!