I'm also curious about these matters. I was there from 1973 to 1986.
As far as I know:
a) the three Khazzans are still in use,
b) the two Maimaa floating storage tanks (as you say, modified tanker hulls) are gone, replaced in 1978 by the captive FSO AL WASEL, another tanker,
c) AL WASEL was, I think, refurbished in 2007 but I'm not sure if it's still there today,
d) I believe the two SBMs are still operating; again, I can't confirm such is the case.
I look forward to learning what, in fact, the situation is today.