I have questions then. Do the angels protect the particles as well during the Novus Ordo Masses, or even Black Masses, so that Our Lord is defended from sacrilegious hands even then? So that the swine think they are desecrating Our Lord but they are mistaken because he remains forever unsoiled and purer than virginal snow? But if you say that, is sacrilege even possible then? Is it all in the intention because God can never be wounded, even by our sins? But he was wounded on Calvary when he died for our sins?

I don't think his logic demands that conclusion though.  There seems to be a difference in nature between deliberate desecration, or even culpable negligence, and just God protecting us from needing to do the impossible.

Yes.  This was the position of pre-Vatican II canonists Noldin and Schmitt, that God would take care of matters on that level.

For whatever reason, God sometimes allows desecration of the Blessed Sacrament.

Even if I don't know exactly why, I think I can make some sense of it.

In a similar way as Hell, the ability to intentionally (or through gross negligence) desecrate the Blessed Sacrament seems like a logical consequence of free will.  Not that God *has* to allow this, by any means.  But its comparable to the Problem of Evil in a way, and just like evil is allowed (in the same sense you're talking about).

That's diifferent than allowing "desecration" for literally no purpose at all just 'cause of tiny, microscopic specks that can't be seen

What kind of altar stone did priests use during the war when they offered Mass on the hood of a jeep?

They used a portable altar. And they had the appropriate dispensations from their ordinary.  

These limitations were formally incorporated into the 1917 Code of Canon Law (Canon 823.2):

“In the absence of an altar of his own rite, it is fundamental that a priest can celebrate his own rite on an altar consecrated in another Catholic Rite, but not on the antimensiis (altar cloths) of the Greeks.”

In spite of these prohibition, however, many exceptions and indults were granted to individual bishops and priests and to missionary societies to use a form of antimension to celebrate Mass on portable altars.

During the Second World War, the Holy See granted to military chaplains the privilege of using for the celebration of Mass, instead of the Latin-rite portable altar stone, “a veil which had enclosed, and well fastened, authentic relics.” This was later extended to peacetime military activities. Since it was not always possible to obtain a veil with authentic relics, the use of an Eastern-rite antimension was considered an acceptable alternative.

Outdoor Masses?  I’ve been to a number of these. 
As a child while on trip across country trailer trip in 1965. Many larger National Parks held religious services for different groups in park amphitheaters.  There was usually a large, open-front building or platform with a covered roof to prevent problems such as you describe, but people had to sit fully outdoors, bring umbrellas if in rain.  In that case, my Dad would usually find a real church, if at all possible.  Depending upon the state of the diocese or the priest, the Mass in 1965, might be anything from fully Latin, ad orientum, to practically novus ordo.  One memory, in Grand Canyon Natnl Park, Mass was in the amphitheater. A no-nonsense priest who said Latin Mass, put up signs re: dress modestly, women cover heads. It was beastly hot, so we brought umbrellas for shade.  A problem became evident from the start.  The covered stage area had barn swallows nested in the ceiling beams who did not appreciate the Mass.  They kept dive-bombing the priest and altar.  The priest requested two men to stand guard duty on sides and keep them away.  My Dad volunteered. He stood there with a broom waving it around to chase the birds.  At the end the priest thanked the men, but announced that Catholics would need to drive the 40 miles to the church next Sunday.
There have been outdoor Masses on Pigrimmages, outside of locked churches where the novus ordo forbade the SSPX from using the buildings.  I’ve been to a Mass in a huge tent, at a group campsite where the picnic table was used for the altar.
I’m sure the American martyrs held Mass Mass outdoors.  Think of those who say Mass on battlefields or atop jeeps during wartime.  
NORMALLY, Mass should be said in a Church, however.  It is wrong to have Mass outdoors or in an odd place just for the novelty.