Can a Texas employer reduce your hourly pay by one third after 10 months of employment without ever informing you that your work is lacking? No evaluation or complaint. This is the agreed upon holy age. This only happens on the day after I return from a 7

I work for a small company family owned. I was hired for $30 per hr with the agreement that I needed training in certain areas. But I was hired as the electrician/safety coordinator. After numerous attempts to get tools needed to do the safety I was told NO.
So I just acted as electrician and tech. I needed an injection in my back and waited 9 months before have the procedure. I always informed way in advance. I had asked for a 90 day and 6 month revue. Never got any. Last procedure done I missed 7 days of work w drs excuse. The day I returned, boss asks me what was going on and I explained. He said this has nothing to do with that, but we are gonna drop your pay from $30 to $20 per hr. I said no. I asked why this hadn't been addressed before now. No answer.
So my question is is this legal? Small company of about 20 people and I know this medical stuff is going to increase their premiums. But even still we agreed on an help wage and I tested into position and so they knew my capability. Also, the owner asked me a question you should never ask in an interview. "How long do you plan to work? Where do you plan to be in five years? ". I was 47 during interview.