How do you set inertial FOR and how do you know it is not affected by UA?
Drop something. Or jump. There you go: an inertial FOR.
If an object is not experiencing an acceleration, then it is inertial.
How do you determine what is in direct contact with UA and what it is not?
Simplified answer (applicable for most things on the FE and most celestial objects; this list is also FOR dependent):
1. Is it accelerating at a minimum of 9.8m/s^2? Yes, go to #2. No, go to #5.
2. Is there an acceleration vector normal to the FE equal to #1? Yes, go to #3. No, go to #5.
3. When the object is not in contact with the FE (directly or otherwise) does the object retain the acceleration described in #1 and #2? Yes, go to #4. No, go to #5.
4. The object is affected by the UA (what I have termed Dark Energy).
5. The object is not affected by the UA/DE.
If the disc acts as a shield to neglect the UA effect, why the Sun and the Moon do not fall onto the Earth? They are over the disc and UA is affected by the shield...
The FE creates a type of 'bow shock' within the DEF (Dark Energy Field). This prevents the objects on the top of the FE from being directly affected by the UA/DE. The field has nearly fully collapsed at about the altitude of the Sun and Moon, allowing for their suspension above the FE.
Last question. Why the Earth is accelerating upwards so regularly (perfectly upwards), but there are plenty objects that are not?
Well, if the FE was not accelerating 'so regularly' we wouldn't be around to know it.