There are always risk in 140 application. I am not so confident especially when I heard some strong cases got denied. If my I-140 is not processed smoothly, then there is no way to renew his EAD based on EB immigration.
However, we are confident that he can get OPT or H1, which will start soon. That's why have been pondering above questions. Again, thanks for your input.
Retrogression really causes troubles to many of us.