This post is 8months old at the time I am writing this reply, so it could be that the AI has been updated/improved since the OP.
If not, there are mods which one could run which are meant to improve AI behavior. Have a look on armaholic.com.
Some examples of such mods are:
Fire-Fight Improvement System
But you'll just have to experiment ...
I will address your question in the realm of Counter Strike since it is the game out of those you listed that I am most familiar with. Take it with a grain of salt since not all FPS games are the same.
If as you stated in the question you are moving and shooting, in CS it is quite possible that you would miss a target, even at close range, due to moving ...
After you initially place the marker, but before you save it, you can:
press Up/Down arrows to change the marker icon
hold shift with Up/Down arrows to change the icon color
Your marker's visibility setting will be defaulted to your current chat channel. For example, if your current chat channel is set to Side, then your marker will be visible to ...
You probably already know this, but for future reference... the UAV you have doesn't have any guns, just a laser pointer. Lase your target and the other team will start firing at them. If you turn on infrared you can actually see the laser dot.
Assuming you have registered properly and are now trying to provide the Player ID information you need to go to your profile in Arma 3 by selecting Configure and Profile from the main menu. Your player ID is displayed there and can be entered into the appropriate location. Make sure you add the  around the number however or it will appear invalid.
Well sitting down playing games all day wont help :P
In my experience of playing Arma, going into prone can speed up the recovery of stamina, no idea why it just seems to work. The stamina in Arma 3 is affected by many things including the terrain, but more crucially the weight of your soldier. Therefore, the heavier you are, the faster your stamina ...
Here is the official 'Experimental Port' page. It explains that you should go to the Steam page for the game, purchase it, and it will automatically download the data for Mac or Linux, depending on the platform you are installing from.