I got 1210 on my SAT and a score of 6-5-6 on the essay. I do not want to take my essay again, it’s too much to deal with 
But I am working to improve my composite score. Can I send the composite score from the test I am going to take, and then send the essay score from the previous test? How much is that going to cost me though?
No. If you send the score that has the essay, then you are sending the EBRW and math scores as well. You cannot send just the essay.
The essay score is fine.