good question! I saw Eurasia poll recently (asked largely of traders and investment pros) and if I remember well the premium was deemed to be less than $5 (when barrel was $60). So I guess it is somewhere in $5-$10 range ($10 assuming that all tensions in Middle East would go completely away - which is never going to happen). What is the fair premium if things go awry is anybody guess though. I can easily imagine WTI @ $100 if Hormuz gets closed for more than few days - but this is unlikely given the strong US/UK presence in the Gulf.
Eh, you're thinking stocks. MMs can trade energy futures on the CME any time they want. However, it's hardly worth their time to do so at 7pm.