So far good news is that they have not found anything wrong with Tyson. Let me know when you hear back about the blood tests.
I have an 18 year old kitty myself and can relate to what you are going through. I ran to the vet with her just a couple of week ago. She has kidney issues and I having been giving her fluids every day for the past three years.
I am glad that OW was out of the office. I am not surprised to hear that she is a sad excuse of an office manager. I find that people that screw in one part of their life tend to screw up in other parts too.
Give little Tyson a hug and lots of snuggles for me.