I'll try to answer them one by one.
#1: Being that you are a high myope, your left eye is presdisposed to retinal problems as well. High myopes have longer eyes, but the same amount of retina as most people. This means that the retina is thinner in the perphery. You may also have lesions called 'lattice geneneration'. These lesions have firm attachments to the vitreous
and when you eyes moves the vitreous, can cause stimulation (flashes).
#2: The heatwaves you are seeing can be you seeing the material within your eyes. The vitreous is in the middle of your eye and is about the consistency of Jello. In the right eye, it was removed during the surgery and filled with a watery fluid (initially a balance salt solution, but now filled with aqueous fluid that the eye naturally produces). I have not had patients comment on seeing the fluid, but it makes sense that it can be visualized, especially in dim light or low contrast light (such as thunderstorms, cloudy days).
Now why in the other eye? In high myopes, you can have an early liquefaction of the vitreous (like jello when it is left outside). So it likely the same thing that is occuring with the right eye. You are looking there a more watery substance and can see the fluid better. Bright lights cuts through the watery stuff and clears it up.
#3-5: This is likely due to stimulation of the retina. When you eye moves, the liquid vitreous moves as well. It may lag behind a bit (likely accounting for the 10-15 second delay). You still have vitreous in both eyes (just less of it in the right eye) that is still connected to the retina. So movement of the vitreous will cause stimulation of the retina. Now, if you notice a change in the character
of the flash, then it may mean the retina was not only stimulated, but could have been torn. Then you'll need a repeat exam to verify that there is not damage.
#6: Phosphene is defined as the sensation of light without actual light (aka flashes). This could be due to the surgery. You have a sceral buckle that likely encircles your eyes 360 degrees. You likely also have extensive cryo (areas that were frozen) as well as areas of internal laser. The retina/photoreceptors are not completely dead those areas. At times, they can misfire and causes flashes.
I don't think your light avoidance after the surgery is a cause. Also, if you are left in the dark for long time, you mind can play tricks on you and start to see light (trying to trouble shoot why it is not seeing).
Phew... I'm still happy to clarify if needed.