Visitor Visa - B2

Friends, We had applied for my Mother-in-Law's B2 tourist/visitor visa. I'm on H1 since 6 years last visited India in 2011.
My wife is home maker on H4 visa staying with me. We have validate visa status till 2017. Following questions were asked to my mother-in-law:

VO: Asked passport
MIL: provided.

VO: Is any relatives staying in US?
MIL: Yes, My son-in-law (SIL) and daughter.

VO: What does your SIL Do?
MIL: Working in xxxx as xxxx

VO: what does your daughter do?
MIL: She is Homemaker.

VO: Asked for my income docs.
MIL: Gave all docs. (tax, paystubs, employment letter)

VO: why is your husband not going with you?
MIL: He is working at xxxx and is not able to make it visit with me.

VO: How long you indent to stay?
MIL: 3-4 months

VO: Do you have any other child?
MIL: Yes, I've yonger daughter. She is studying.

VO: We cannot provide you visa based on certain law and here is the document for the same - which was standard 214a refusal statement.

There was on discrepancy in the I134 document and invitation letters I had mentioned that I shall pay for her travel expenses. But in the D160 it was mentioned that they are going to pay for the same. Anyhow, this question wasn't raised and I134 wasn't reviewed. She carried my Father-in-laws I.T return and other financial docs but there were not asked/assessed.

I'm planning to reapply for her. Have got following questions:
1) Should I have my Father in law also apply along with my Mother in Law?
2) How sooner/later should I apply? (can be done in couple of weeks period?)
3) My wife is pregnant, so we declare that as ONE of the reason to visit besides tourism and socializing?
4) Any other suggestions, tips, advise are most welcome.

Kindly respond to me only.
Thanks!