Learn English – feel disgusted vs feel disgusting

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)

Your first example is not correct. "I feel sadness" is not good English. You can say, "I am filled with sadness," or "I am overcome with sadness," but when you use a sense verb like "feel," what needs to follow is an adjective.

Similarly, we say "I feel tired," not "I feel fatigue." "I am overcome by fatigue," on the other hand, would be correct because "to overcome" is not a sense verb.

See: https://www.grammarly.com/blog/sense-verbs/