Sounds like the second shop you went to was not as reputable as you first thought. I’d dump them and see if you can get some new recommendations from the 996 crowd.
Were any of these symptoms present prior to your original “low fluid” code issue?
It sounds like you have several different issues.
A common (& easy) DIY repair for electrical issues is the replacement of the electrical portion of the ignition switch. When these go bad they typically cause all sorts of strange gremlins. Porsche recommends changing the entire electrical and mechanical portions of the switch but I and many others have had good success with just changing the electrical portion. Our host has them & and their cheap (~$15.00) and easy to replace. If you are in a rush you can also get them from your VW/ Audi parts counter.
Porsche 996 Switches & Motors - Page 1
Someone here will chime in on the proper part #, as there looks like two options. When I did mine there was only one choice. The switch takes less than a half an hour to replace. Google “Porsche Boxster Ignition Switch Replacement” and you’ll find lots of DIY instructions.
I only mention replacing the ignition switch because it a common failure that can cause several of the issues you mention like dash lights not working. It’s also quick, cheap and easy to replace and may either fix some of your problems or at least eliminate the switch as a possible contributor.
As Wayne mentioned you need to find a shop that has a PST-2 (Porsche System Tester) and knows how to use it. They should able to find/isolate the problem quickly. If your car is taking a long time to warm up it sounds like the thermostat may be stuck open, but this is just a guess on my part. It’s more likely something else as the car shouldn’t run rough or throw codes simply because it’s not up to temp yet.
P.s Great looking car, good luck and hope you're back on the road soon.