Minecraft – way I can testfor an entities coordinates, then use /tellraw to put the coordinates in the chat

You can spawn a redstone block a certain numbers above or below the point of the player with an activator rail ontop. Then spawn a command minecart on the activator rail with the command /spreadplayers ~ ~ 1 false @e[name=PlayerHome,type=ArmorStand,c=1,r=2].

Because the /spreadplayers will load the chunk the entity is spread to, the commandblock minecart on the activator rail will permenantly keep the chunk that the armorstand is in loaded. When moving the point, run a fill command and a kill command at the previous home to remove the traces. When you are teleporting the player back to their home, you can simply offset the teleportation by a few blocks in the y coordinate.

You can use scoreboard in player selectors to find out which one they clicked. Usually this is done by either testfor or execute.

I recommend a 20 t/s clock to check these as soon as they click it. You don't have to use one, but it may help. great method to setup one.

In the case of testfor, it is actually not recommended to use it. You can't exactly distinguish which player clicked it, you just know that it was clicked. A better way is the execute method. Never-the-less, the command should look like this:

Testfor @a[score_test=1,score_test_min=1]

You will need a comparator to get if it succeeded to find it. You should also have a separate command block for each, then change the 1 to another number for each possible outcome.

In the case of execute: recommended method. You can use @p in the command part to target that specific player. Command as follows:

Execute @a[score_test=1,score_test_min=1] ~ ~ ~ <command>

For this, you should set their score of that to 0 as soon as the command is run, otherwise that command may be run twice.