well, to answer you questions...
I get headaches to from starbuzz, if I smoke constantly without a break. Its a very easy to smoke tobacco so you can put too much heat on it and not even notice.
Now your bowl is shallow, I have heard the more shallow the bowl the more towards the edge you need the coals, the deeper the bowl the more towards the center you can place the coals... works well for me too.
The size of the coal seems huge for the bowl. I'd break it in half, put the two pieces on the edges of the bowl. Make sure the coals are well lit (red all around, no major black spots). Even not quicklite coals leave a flavor if they aren't burning completely.
My shisha pretty much always touches the foil to some extent. maybe it burns out faster than it should but I can usually smoke 2-3 hours with flavor. Remember not to use too much coal and to rotate them when you ash or add new coals.
That dirt as you say in the pictures looks like calcium build up. Is your water hard where you live. To remedy that You want to make sure when you clean your hookah you let it dry completely don't have water standing in the stem or base. I had a base like that and the corners were caked with calcium... If its calcium you can remove it with the proper cleaners, I won't tell you how to do that, find out yourself, it would take to long to go through all the procations just make sure you rinse it out very very well afterwards.
different shishas require being packed differently. Fumari for example need to be very sparse and lightly packed, Tangiers needs to be densely packed(even compressed). I've never noticed any issue with starbuzz, so I'd say just pack that sucker full.
On a final note, I personally hate round coals, I can't seem to manage them, the explode or break apart when moving the, and don't seem to stay long enough. I prefer squares or even better fingers broke into smaller pieces. Naturals are difficult as you need to keep them stoked or they will stop burning, I don't have the ability to deal with that, so I tend to stay away from them.