My question involves defamation in the state of: TX

I am a small business owner.
18 months ago a client had (in his opinion) a negative experience with my business. He proceeded to post multiple negative reviews about my business on several different websites. Although they were malicious, I would still consider them protected because they were his opinion. I was successful at getting a few of these reviews removed from their respective websites. I reached out to the individual once to offer a refund of their charges in exchange for removing his reviews, and he refused.
I have had no further business dealings with this client since the first and only encounter.
This previous month (over 1 year has past), the same client posted a new round of reviews that were even more negative and malicious than the originals. The exaggerated negative comments actually contradict the comments made in the previous year's reviews:
- the first review said I answered most of his questions, new review said I ignored him and didnt answer any questions (I have screen shots of all reviews)
- first review said that I contact him once asking to remove the review, new review said that I contacted him multiple times asking to remove the review (I only contact him once and have records to prove this)
Looking at his list of Yelp reviews, there are multiple 1 star reviews using malicious and inflammatory words to smear the business' reputations. In several reviews, the owners have responded to dispute the details of the review. For example, in one instance the person claimed to have waited many hours, and the business has a time stamp of checking in and leaving after 45 minutes. This shows a pattern of behavior and may support my claim that the person lies in their reviews.
SO, my question is whether the discrepancies between the old and new reviews on my business would provide adequate proof that this client made false statements in their review. I don't know how to get rid of this person, and am hoping that the threat of a lawsuit would deter any future online disparaging of my business.