Learn English – the difference between ‘use’ and ‘apply’

If a man is drowning in the water then he should have faith / hope that somebody will come and save him.

If this man has a strong hope that somebody will save him, he still allows for the possibility that nobody will do. He is very hopeful, but he's still only hoping. If he suddenly feels some doubts about his hope, he may dwell on these doubts, because hope does not forbid it.

If this man has a strong faith that somebody will save him, he refuses to admit even the possibility that nobody will do. He may feel some doubts deep inside but he will suppress such doubts with all his willpower, because he has faith. Entertaining doubts would be a betrayal of his faith.

Hope is often based on mundane inferences: "I read in newspapers about drowning people being saved. I know that there are boats often crossing this part of the river (lake, ocean)."

Faith is often based on the supernatural: "I have a guardian angel, he will make some fishermen notice me and hurry to the rescue."

P.S. This is really a philosophical question. You might try asking it at (on?) Philosophy Stack Exchange.

In your first example, you would just use above, as an adverb is all that is needed. But it really only describes what is directly above.

In your second example, from above is not helpful because it is not specific as to what you are referring to. You should point to the specific location.

When using from above, from is a preposition, so I expect an object in that phrase. For example:

From above the trees, I could see the distant horizon.

The locations are specific. Also motion is often involved:

The birds flew from above the trees to the roof of our house.

There are some idiomatic usages though, for example:

Their new baby was a gift from above. (meaning from heaven)