Growing apple trees, lessons learned so far

I am in Coastal SC and have had no luck with any kind of fruit tree apple trees got one Dorset apple and its been in the ground 20 years and when it puts apples on they are the size of golf balls. Had a granny smith put apples out one year and died. Plums did well then have some bug gets in the fruit can't get ride of them. Have resorted to growing citrus trees in big containers, get plenty of oranges and limes and lemons

 

Spray those plums with water laced with dawn dishwashing detergent and Louisiana hot sauce

 

After about a week under the shade cloth my trees are doing better than ever and can't even tell damned deer ate most of the leaves off those trees.
The heat ravaged leaves stopped turning more brown and it's covered with fresh leaves.