Defamation cases are tough to win, especially if you cannot show any monetary damages. In most defamation cases you MUST prove some harm. Realistically, there's no value in spending tens of thousands of dollars on litigation if you can't recover more than that in damages, so the harm is going to have to be quite severe. In a few situations you do not have to prove the harm, it is assumed by way of the content of the defamatory speech. These include false statements that result in a criminal charge of a crime, falsely stating you have a "loathsome disease" (think STD), or it is directed at your job or business. Even though you do not have to prove harm occurred in these three cases, realistically a jury is going to try to quantify how much to give you based upon what harm you caused. If nothing serious happened, you will probably spend more money on litigation than you would recover, which is why attorneys are generally unwilling to take the case on contingency unless the proof of harm is very clear and the degree of harm is severe.
You mention that it cost you your photoshop expert. Is this related to a business you have? Have you had an actual loss of business, such as losing contracts for work, because you do not have this expert? Do you have proof that is why the expert left? If you have substantial business losses that are clearly tied back to these statements you may have a case that is worth the cost of litigating.
The other hurdle you have is proving the statements are false statements of fact and not merely unkind statements of opinion. What qualifies as opinion is very broad. For example, if the statements you refer to said your work was garbage or you don't know what you are doing, those would be statements of opinion even though most people would disagree with those statements.
Perhaps your biggest hurdle is the question of getting paid. If you can put on a fantastic case and prove to the jury that you have tremendous damages and they award you hundreds of thousands of dollars (just taking a number out of thin air), it doesn't matter if you cannot collect the money from the person posting these comments. That's another reason why lawyers don't like to take these cases. There's usually no way to get the money out of the defendant, unless the defendant just happens to be very wealthy. Under Texas law you will not be able to go after a person's home or vehicle to collect on a judgment and those tend to be the two most valuable assets us normal folk own.
You might have some other options available to at least try to make this other person stop posting additional comments. It's not as juicy as a defamation suit but better than being stuck with these comments continuing to show up on Facebook.
Another thing you need to know is that if you do sue somebody for defamation and you do not have a reasonably solid case you can actually have your suit dismissed and have to pay the defendant's attorney fees plus additional money as punishment for trying to use the legal system to silence somebody for criticism when it was apparent you had no case to begin with. So that is something you really want to think about if you decide to move forward without an attorney.
You probably don't want to post any more facts about your situation online. If you would like, you can email me at firstname.lastname@example.org and let me know some examples of the comments being made and how it is affecting you. We might be able to craft some favorable solutions.
Let it go. I understand that this is emotionally upsetting, even more so because its someone you once cared for, but without provable substantial damages, it simply isn't worth it, to you or to an attorney. Report the abuse to Facebook and then move on.
This is general advice and does not establish an attorney-client relationship.
Sign up to receive a 3-part series of useful information and advice about personal injury law.