TG80:
Generally when the charges are set off the conditions in the well will protect against the ignition of any of the hydrocarbons around the charge. To ignite methane, for example, the amount of methane in the air has to be within a finite range, too much or too little and it doesn't happen.

That is not to say that there can't be fires in hydrocarbon deposits underground, though they are mainly in coal and coal mines such as, sadly, the disaster this week in China.

While I have seen the occasional picture taken from within an underground well I don't think that they are that common, and since the penetrating charge is going through the casing into the rock, the picture might not show a lot (though more if the hole was still open, i.e. had not been lined).

Yes proppants really work (at least the vast majority of the time) though there are some conditions to their use that I might get into in a later post. There has been a lot of lab work where tests were carried out at the same pressures as deep in these wells to validate that the results can be, to a degree, predicted, and then there are the actual practice in the fields where the production of natural gas/oil that would not have been obtained at that level without the proppants is an indication of the success of the tool.

TG -- No chance of explosions or fire...not enough oxygen down there to support such events. We actually do have a secondary oil recovery technique (in situ combustions aka "fire flood") that does burn oil in the reservoir but we have to pump oxygen down there to make it happen.

As far as imaging the frac results we do have a system similar to a seismograph survey. We actually can "hear" the rock cracking and place those sounds in 3 dimensions. It's a rather expensive effort and a tad complicated. But I've seen amazing results. One operator had fraced a zone and modeled that the frac propagated out in a certain direction. In reality the frac didn't even go into the target zone. It went into a completely different (and non-productive) formation. Imagine trying to analyze the results of fracing Reservoir A when you didn't know you had actually fraced reservoir B. It's a great system but expensive and often difficult to justify to management the need for it.

Propants: No Propants...no frac jobs. Cracking the rock open doesn't do much good if you can't keep the fracs open.

#4: Not exactly sure what you're asking but in general NG moves much more easily then oil through a rock or a fracture. A surface tension factor.