I've seen the cracks on citrus before and I don't believe they indicate anything other than growth. However, the lines on the leaves are Leaf Miners; not a good thing. You try treating the leaves with the usual mix of garlic and soapy water, but I can't swear that will work.

Leaf miners are no cause for concern . Growers simply ignore them . Leaf miners live between cell layers and are not touched by surface sprays .

From the link below :
" Citrus leafminer generally does not noticeably affect growth and yield of mature trees. Biological control through natural enemies already present in Florida and the introduced parasitoid wasp makes a significant contribution in suppressing the problem. "

As for the cracked trunk ... not sure what it is other than drought , hurricanes , drought , flooding from Fay , excessive heat , coldest winter in 25 years , drought , heat -- you get the picture . A mature citrus tree can live 30 days or longer with no water at all . Watering once a week is probably enough until the rains return - if they ever return !

Get your tree on a regular fertilizing and spray program . You can do this organically - no need to use harmful products unless it's necessary . Read through the many links on citrus at the link below :

Here is a link that might be useful: Citrus Problems In The Home Landscape

is it just cracking or does it feel like the bark is sluffing off there? It could be foot rot perhaps. do you have a sprinkler pointed at the trunk at all?

That's not what foot rot looks like. I get those vertical crack lines on my grapefruit tree, although not that pronounced.

Christine