naanshi,
I think you should convince somehow to your client about risks of using EAD before the approval of I-140 .. Tell him that when you applied for I-140, the way things were going, you expected the I-140 approval by 5 months, but it is now not the same..
Ask your client to consider to wait for 2-3 more months to accomdate any RFE if you get one (I sincerely wish you will not get).. May be you can take a bit less salary to convince him(if he is a desi company)
Also according to the scanner I did not see any denials in the I-140 in the whole of last month,, so I am guessing eventhough so many RFE's are coming up now-a-days, the denial of I-140 is very very rare( I guess unlikt you applied in texas, this time everything regarding I-140 that you filed is strong).
My guess is that, the officers probably that may start by next week(those coming from H1-B) would be experienced enough to approve I-140 without any RFE's//
Don't loose hope "try your best", and leave the rest to GOD.. whatever happens will happen..