Lato,
I have few questions:
1. Are you a US citizen? or a permanent resident?
2. Is your spouse in valid H1B visa? 
3. Is your spouse currently in United States?
4. Do you want to file under family based category (I-130) i.e as a spouse of a US citizen or a permanent resident? 

Regarding your concerns:
If your spouse is currently working in US in H1B and the H1B will still be valid for another 7/8 months, I don't see any reasons to file I-765. The other thing is: you can file I-765 any time while your case is pending ( if you need), at no additional cost. However, it might take 2-3 months to receive EAD card once you file I-765. If you file I-765 along with I-485, it doesn't hurt you. Your spouse can continue to work on H1B, do not use EAD until you need it. 

I think G28 should be filed if you are using an attorney. I am not sure about DS157, I don't know where you saw it and why do you need it. May be some experts can comment regarding the forms G28 and DS157.

(IMPORTANT: I am NOT a lawyer. This is my personal opinion and should not be used as a legal advice)

- Jangali Maanab