You should not have paid him even half the fee for a lousy effort. That is what made him brazen enough to demand full payment. When you do not have the intention of using the paper at all, you should not pay the writer. When a writer does not meet the writing requirements and client expectations, he should not be paid. No writer should be paid for unsatisfactory work. What you did was reward bad behavior.
I bet you did not even complain and tell him that you will not be using his shoddy paper. Since you did not use his paper even partially, you can safely ignore him. Having your details will be of no use because, even if he convinces a professor to check your work for plagiarism, which I doubt he can accomplish, the professor will see that your paper is 100 percent original and legit. He will trash the report for sure.
Sleep soundly tonight. You have no problems to worry about with this Kenyan. Do not forget to block him on social media to avoid further harrassment. Report him if possible to ensure he cannot victimize anyone else.
Can you share his name here or his social media number / identity so that the other students can be warned of this fraudulent writer? It would really be helpful to all concerned.