how long will H1-B visa stamp valid(6 months) and how many entries now?

my current immigration status is I-140 approved, but cannot file I-485 because of the backlog(EB3). Currently I am on extension of my H1-B beyond 6 years.

I have few questions:
1. is it OK for me to travel back to China for short visit? My immigration attorney said there is no law prohibiting me from traveling outside US, but many Chinese friends said it is risky, there is a chance I may be denied visa(H1-B) esp. considering my current immigration status. Wonder how risky it is really? Anybody will similar situation?

2. I went back to China in 2006 under h1-b and applied for h1-b visa stamp in Shanghai and got it, if i remember correctly, that visa stamp is valid for 3 months and 2 entries. Is it still true(3 months and 2 entries) now with H1-B visa stamp for Chinese citizen?