Above UFL??

in theory there will be no combustion, however you can get variations on concentration and if an ignition source is there, it may just have a spot below the UFL and ignite and the heat will drive the reaction onwards.

Obviously the limit is zero air = nothing will burn and the other is zero fuel = nothing will burn

As a first approximation of the oxygen content required for combustion when the oxygen comes from a source other than air, you can convert the flammability limit in air to an associated oxygen concentration. Air is normally 21% oxygen. Flammability limits are valid for systems at 1 atmosphere at room temp. Elevated temperatures and pressures may change the flammability limits.

If the only reaction that can take place in your system is the reaction with oxygen, once the oxygen is consumed, there will be no more heat given off. While a tiny amount of pure oxygen that is locally concentrated will burn if it it has an ignition source, you have to evaluate whether this creates a condition you are concerned about.

I'm not sure I really understand your question.

Oxygen will make anything burn if you get it rich enough. That includes metal.

Any chemical or substance will have a Material Safety Data Sheet available for it from the vendor that produced it. They are to provide that with the first delivery and any time upon request.

The MSDS will have flash points and flammable temperature levels listed, along with any kind of protection needed when handling the material and what chemicals that it is not to be stored near and clean up procedures if it should spill.

As the other poster suggests, it shouldn't burn above the UFL, however if it is a vapor cloud in the air, obviously mixing, the edge of the cloud, etc. are all good spots for an ignition to occur. Flammables in any concentration in the presence of oxygen represents a dangerous situation, hence the rigorous controls that should be around a fired piece of equipment. Even your propane grill.

Yes, the range is higher in oxygen rich environments, simply because there is more oxygen to oxidize the fuel. Anything above 23.5% oxygen is considered a potential fire/explosion hazard, I believe. There is a famous demonstration of this where a professor at Purdue University used liquid oxygen and a cigarette to get his charcoal grill going. Anything will burn in an oxygen rich environment, be extremely careful.