If I read your info correctly, the totality of the circumstances looking from the CO's perspective is that you have been wavering around the poverty guideline (above and below) since application, which would not instill confidence. One of their primary concerns when reviewing is that your sponsored alien does not become a burden to the State, as in they don't end up on welfare or similar. Your wife's Philippine income is irrelevant, as she is not the sponsor and will have zero income when she gets to the States. If you have a "6 figure written job offer", why didn't you accept it and end this question about your ability to support? The totality of the circumstances is that you are retired on social security with a young wife and two elementary school age stepchildren who will be living at around the poverty guideline level. I'm not trying to be harsh, just realistic. Just keep doing and providing what they ask and eventually you will prevail. Best of luck!
Both are major life decisions, child and immigration. If you wait with having a child there's a strong chance you will not be able to conceive. Having a child before you actually travel may add a delay to the process, but you'll still be able to get the visa. That way you have both a child and your visa. Don't wait with having the child.