... I went to the LBS and explained I was ready to try tubeless on a bike I ride mostly on gravel. We decided on 700 x 42 tubeless-ready tires and tubeless-compatible wheels. ....
...When I picked up the bike, I reminded the LBS owner that this would be my first time with tubeless and asked him to recommend a patch kit. He handed me one and pointed out the bottom of the patch kit carrying case was a wrench to remove the valve cores. He told me to add more sealant every four or five months and said not to go over 60 psi so I don't blow the tires off the wheels.
OK, I'm going to stir the you-know-what a bit. You went to an LBS instead of embarking on the research and didn't have the know how to do it yourself. Please understand, this is not a criticism on my part, but just to say that I will assume you paid more for this set up than you would have had you spent the time and effort to do it yourself. A fair exchange, had they given you what you paid for.
You reasonably expected expertise and you were willing to pay for it to get the job done right with a minimum of hassle and uncertainty on your part. And, you clearly explained your goal at the beginning, and you again clearly when you picked it up.
I feel you were very poorly served and actually misled when you picked up the wheels. There was an actual cost to you of their poor service, maybe not in terms of money, but in terms of objective, significant avoidable hassle to you and your rescuer. You will need to deal with them as your personality sees fit, but anger would be a reasonable response. This is just a very incompetent, poor service by the company and they need to make it right and in some way compensate you for their misleading you and the significant cost / hassle you experienced on the trail. In no way did they give you what you paid for and would reasonably expect. I would be pissed if they turned around and charged me anything to properly set up the wheels and tires tubeless, including giving you some free sealant for future use.
I won't call them a poor excuse for a shop or that they ripped you off, but it's close, imho. But an example of why LBS's aren't always worth what they and their supporters claim.