While I'm not an arborist, (yet), I have been growing my own citrus in my back yard here in Orlando, Florida USA, for the past 5 years and I went through similar problems, at least with the splitting. I found a pretty good paper from the University of California, at this address here.
http://homeorchard.ucdavis.edu/8038.pdf
Generally attributed to stress and watering inconsistencies, the rinds become rigid and can't expand with the fluctuation of water/sugar flow into the fruit and the rind splits open. Read through the file and it will shed a bit of light on how you can combat this. Although, since you aren't there that often, you may have to hire someone or set up an automatic watering system.
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My citrus: Blood Oranges, Ponderosa Lemons, and Plain Navel Oranges. The lemons grow as big as your 2 fists together some years and no longer split since I've kept the watering consistent. I had a problem with leaf miners a few years ago but haven't seen them since I used some citrus based insecticide recommended by my county horticulturist.
here's an example of what the miners do to the leaves.
Like I said, I'm not a pro (yet) so if any of the other folks see me saying something incorrect, please let me know. This is just what I've experienced in my own yard.