Here is a quick rundown of my situation:

Husband here on K-1 in May 2005
Married June 2005
AOS approved 2/16/06
90 day period to file I-751 starts next week 11/16/07

We have a 15 months old child, I also have 3 other kids.
We have had a tough time as did not adjust well to this culture or marriage responsibility
He left me for 2 months while I was pregnant to visit his family in his country
He returned for the birth, I support him pretty much fully from last July to this past May, when we separated and he moved out (though he never formally changed his legal/mailing address- he was only a few miles away
He moved back in in October. We have good days and bad- trust is seriously damaged as he has cheated on me a he knows I have proof.
I have a hard time drawing the line because our baby loves having him in the home
When he moved out I filed for child support because he had never given me a dime for her- for the hospital, diapers, formula, babysitter- nothing.
In late Sept I got a child support order which is now in effect- it come out of his check and direct deposits in my account
Even though he is back in the home, this continues and I refeuse to suspend it
All our things are separate- bank accounts, credit cards etc, though I do cover him on my health insurance.
Mortgage and deed are only in my name.
We have fotos, but not a lot of solid documentation-type support.
To make matter worse, he's planning to go back to his country for a 4-5 week vacation in January/Feb, right up to the date that is Cond GC expires. IMO this sucks and doesn't say much for his return to be good husband and father. He still doesn't contribute to househodl expenses except food. Also if we file soon isn't there a good change his biometrics appointment will fall during this time?
I pay everything, take care of our child and my 3 others and maintain the house inside and out alone.
He's also no help in preparing the I-751 package- though he expects me to do a bang-up job. If we have problems he will think I sabotaged the process somehow.

Questions:
Will the baby outweigh the lack of a lot of other documentation in the approval decision? Does anyone with a child ever get denied?
Will the child support and arrearage (back there's a back support order for $1500) come up in the name or whatever opther check they do?

I assume we'll be interviewed- I don't want to lie about anything and will probably not hold up well emotionally if I have to defend him, because he's actually not been that great to me. I've thought about divorce but still have silly hope that he'll grow up (he is younger than me).

What does everyone think? Any comments/opinions are welcome.

I am not sure what you want. If it were me I could push forward by myself

I could easily push forward by myself, I do it anyway and was happy when we were apart. My dilemma is that although I don't really feel like the marraige was entirely bonafide on his part, I can't come to terms with our child asking me one day why her Dad isn't there, and me knowing I didn't do everything I could to keep them together (in the same country). He's not much of a supporter but he is very loving with her and she is very bonded with him. I guess my plan is to just be very straighforward (factual) with INS and not ask for anything particular, then just take the decision as fate.

While it's true I don't know all of your particular facts, I seriously doubt that an alien that entered a marriage solely to gain immigration benefit would plan to begin a family together. It is possible that the marriage was not really destined to last, save for the child and that is the "glue" that keeps your alien husband and you together. USCIS usually consider a child born to the marriage as good evidence of a bonafide union. Of course, such evidence would not or could not outweigh compelling evidence of fraudulent intent upon entering the marriage, should there be any.

I don't believe that the child support issue will be in any documentation that USCIS would secure, but if it comes up, the alien is advised to answer honestly.