Yes, the C-5 can dump fuel. At his fuel load, about 9000# per minute.
Normally, a heavy weight OEI return would be flown at 40% (apx 16 degrees) of flap vice 100% or 40 degrees at normal weights. Vref would be around 168 or a bit more. The plane, at heavy weights can be "underpowered" on a OEI return, but is quite controllable, if the speed is closely monitored and power is applied correctly. Getting slow is likely to be very scary or non-survivable. Could that have happened--maybe, but the crew was highly experienced and knew what the stakes were. Sims are done quarterly, emphasize OEI work. NOT to imply any faults on the crew, we simply do NOT know what happened.
The thrust reverser, as opposed to FAA-certified planes of like vintage, does NOT mechanically pull the throttle to idle in the event of an uncommanded T/R deployment. With a T/R deployed, they would have shutdown the engine and landed on three. IF a T/R deployed, it would have a either a crash OR a routine return on three. GE and Lockheed have done major work on the T/R installation since the RMS accident and it has been pretty reliable since. While a T/R was the cause of that accident, no other plane has been found with an identical fault, seems to be a one-time event.
A two-engine inoperative landing, assuming they got to a safe altitude (DOV about 1000 feet) would have required careful handling, a willingness to apply near T/O power on the operating engines and good planning. It is possible to return heavy on two, but worthy of a DFC on the part of the crew and the handling pilot. Losing two during liftoff would have been a certain disaster, IMHO. Two engine returns, in the sim, are managable at around 730K weight, but in real life, demand skill and a bit of luck. A perfect sim performance is just like a perfect operation on a cadaver. You will be flying with a bootful of rudder AND full scale rudder trim AND T/O power. There is absolutely no room for error.
From many sim sessions and several three-engine landings, these guys did pretty well with what they had. They got real, real close to the runway with an obviously very sick plane and landed it without fatalities. It had to be very, very damaged, beyond a simple engine-out to result in a crash landing. I await the investigation for the real answer, not idle speculation.
There is something missing in the open news as on now. NO news there.
GF