thanks in advance if any one helps. i have trouble moving the cursor precisely and for most things Tab is my friend but fishing, looting, herb, mining, or skinning I have trouble especially fishing. if there was a mod to enlarge the pick box when doing any of those things or just a way to increase it all the time and adjustable so i could find the correct size that would be awesome!
I'm assuming it was just one of the lower-level customer service reps that sent you here. This is not possible for addons to do. They cannot change or access anything in the 3D world (beyond nameplates, which are a hybrid between the world and the UI). Once a mob is dead, it no longer has a unitID associated with it. I don't think targeting by name works after it's dead, either. The UI has no idea where anything is on your screen, and addons cannot set the location of your cursor to even scan the screen for tooltips as this falls under Blizzard's definition of automation.
I assume you already have it set to loot multiple mobs at once (I forget what the setting is called), and that you have the loot window set to appear under your mouse. If you have a hard time finding your cursor on the screen, there is the CursorTrail addon or Where Cursor (DMouse). But for any of the professions, there is nothing that can be done except to make sure you are zoomed in all the way.
One last thought that is not addon or UI related... You may have done this already, but have you tried fiddling with your mouse sensitivity? Some mice even have a button on them with presets. You could have it set to move at a faster speed, then push the button and it will be slower and more precise.