Summer tomatoes in the south are not easy. The plants do well in spring and will do well again in fall. During the heat they tend to abort blooms and if they set will make small fruit. The splitting is due to a rain or irrigation following a dry period.
I suggest leaving the vines to produce for fall or if you like some minor pruning is also okay. Another option is to take those long vines and bury the ends leaving a foot or so sticking up beyond the buried section. Keep the soil moist and they will root in a couple of weeks. Then you can cut them off from the "mother plants" and remove the mother plants leaving the newly rooted tips to grown and produce for fall.
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