The pitch and volume of the sound are determined by the size and width of the propellers and how fast they are spinning. Until someone comes up with a way to keep a drone in the air without props, you are not going to see a "stealth drone".
I flew two batteries down to 24% with three minutes between flights on the Mavic 3 Pro today in central Alabama. 91 F. No problems.
That "feels like" temperature is increased above the normal dry-bulb temperature to account for the effect of...
I'm usually fine with a little flare. In your video, it's a bit jerky and is a bit distracting. That movement will make the removal challenging as you are chasing a moving target.
The "green dot" appears to be lens flare. There are some techniques for reducing lens flare. There are a few tutorials online and they use variations of the following:
In the Color page of DaVinci Resolve, select the clip with the lens flare...