Here are my H-1B 6th year visa expiry dates:

Passport visa stamp : 07/01/2018
I-797 A : 09/01/2018
Latest I-94 : 09/11/2018

I work full time for a fairly big American company. My I-140 was approved in 2015 (EB-3) and most likely my company will apply for my visa under wage level 2 since I am a little below wage level 3.

I have an urgent need to travel abroad in May 4th week for 2 weeks. I will most likely be left with 3-4 weeks of visa validity on my passport once I return. I have the following questions:

1) Should I opt for premium processing of my case? I have heard that chances of getting RFEs are higher in that, is that true?
2) Can I travel abroad during the fourth week of May while my H-1B extension adjudication is pending? Will I face any issues at Port of Entry during my return to the US?
3) What happens if I get a RFE for my petition? Will I still be able to travel abroad and return as per schedule?
4) What happens if the events abroad don't go as expected and I am unable to return before July 1, 2018 while my H-1B petition adjudication is pending or waiting for RFE response?
5) If my H-1B extension is approved before or during my travel abroad then do I need to get a new visa stamp on my passport before re-entering the US?