L Extension and EAD query

[SB2016]

Could you please address below queries wrt to L1. I have applied for L1B extension and currently it is in progress.
1.On Petition getting approved,what are the steps for Visa being stamped ?Should I go out of US for Visa stamping and what is the approval rate ?
2.My spouse's EAD expires on 16th Dec 2017.Once L Visa extension petition is approved and EAD is filed before 16th Dec,can they continue to work while EAD is in progress?
3.Also is it fine to travel out of US while EAD is in progress ?

Thanks in advance!