As already stated above, if you research old threads on these forums on parameter mods for earlier DJI aircraft, you'll find your answers, assuming that the appropriate parameters still work as before. A lot of them can still be changed but are automatically reset to the original values upon boot up.
This
exactly! The things more rules and regulations are made of. Case in point the PhD educated drone operator who flew 1 1/2 miles away, way out of visual range, toward the recent California fire debacle, and occupied the same airspace with a fire fighting aircraft. Still waiting to see what new punishment regulation is dumped on all of us. Just goes to prove, stupidity can’t be regulated, no matter how many rules the rule makers come up with. Why make it easier to accomplish a new level of stupidity? 
This is a possible factor, maybe in a last-ditch situation. But like meta4 said, Those are things to be aware of, and you have to take into account how weather will affect your flight time and speed of flight. In windy conditions or other hazardous weather, take extra precautions. Don't start returning home at 30%, start back at 45% and avoid critical levels altogether. I have made the stupid mistake of underestimating wind with my air 2. I thought I had enough battery to make it home, and in normal circumstances I would have had enough, but I didn't with the wind. Had to make an emergency landing in someone's backyard, and walk a half-mile to retrieve it.
i modified the value to zero and test flied the air 3 still force land at 15% bat , so this parameter is not for the critical low battery forced landing, am only making a guess that it maybe to the smart rth once the drone calculates the battery level and drone distance and time required to fly back, i hope some one explains those parameters , i will try to do my homework about them in details once i have time
If you were flying a real plane, you would be crazy be planning to land with only a cupful of fuel left in the tanks.
Just for grins, I recently rode my Yamaha CrossCore RC ebike until the readout on the control unit showed an estimated remaining range of 8 miles at the lowest level of assist. At the highest level of assist, the estimated range is far less. There's a steep hill in last quarter-mile or so of my return home. When I reached the foot of the hill, the battery simply didn't have enough juice remaining to provide the additional boost I might expect at a higher charge level. As a consequence, I was obliged to pedal a 52-pound bike up that steep hill. Lesson learned, even though I kind of knew what the outcome would be.
Your assumption that one would stupidly use Sport mode in this situation is unfair and unrealistic. You are the one now who is making simplistic and uninformed assumptions about the OP. DJI batteries also perform very predictably down to their displayed 0% remaining battery. You are also naively assuming that DJI's Remaining Battery Percentage is designed to be accurate, where achieving 0% means it falls out of the sky. Please reread Post #11 above. 0% is not zero. It now leaves a minimum of two full minutes of flight time. Anyone can check the voltage levels on Air Data for flights that reach 0% remaining. Voltage levels are still above 3.5V per cell. Even DJI uses 0% remaining for all their advertised flight times on all aircraft, and are never crash landing! Read the asterisks below the advertised flight times.
There are a combination of three or four parameters that need to be changed, as spelled out in the thread I linked and the others I suggested you search. The Smart Battery parameter is the one that kicks in before forced landing that can be easily overriden. The others you referenced are more relevant. Look at the thread. The OP explains exactly how to do what you want. Here, in this thread, you just are wasting your time. I have already given you all the information you requested. You just have to read it.
to sum up this discussion.. first
Proper training in all full-scale aircraft includes forced landing scenarios. It also includes training in how to prevent such scenarios. Anyone who takes to the skies thinking they never need to deal with forced landings is a fool looking to become a statistic.
Which should include the PIC being able to disable or modify the manufacturer's default specifications for forced landing, to ones more appropriate to their own needs. Knowing how to still control the aircraft and override a forced landing, once it is initiated, is also critical.
