Engines - The Marine Corps always talks about 3000 foot runways, which does seem long for a STOVL - but I suspect that they have realized that they are not always going to be able to operate without an airborne logistics line provided by KC-130s, particularly in hybrid-warfare situations where land routes will be targeted by insurgents.
As for creeping and rolling VLs: I await the demonstration of true improvised-base ops with great interest.