Hi,
POTS IS a form of Dysautonomia. Dysautonomia is an umbrella term that describes a bunch symptoms and literally means dysfunction of the autonomic system. It includes a group of conditions, POTS being one.
I, myself have POTS, and I'm not a Dr, but what you're describing sounds just like POTS. The test you had done is called the poor man's tilt table test, and that is actually how I was diagnosed. You should have been sitting with your feet on the ground, though. The important part is that they waited the appropriate amount of time in between blood pressures, (preferably it's best to take them manually, bc the automatic machines aren't always reliable, but that's not mandatory). I can attest to that from my own personal experience. Either way, the biggest factor is waiting the appropriate amount of time in between blood pressures.
They didn't perform the test right thiuy bc your feet should have been on the ground, sitting in an upright position, not with your feet out in front of you.
Some ppl will say the only day to diagnose is by a tilt table test. That is the golden standard. But the "poor man's tilt table" test is just as reliable and accepted if it's done properly.
You are being treated and managed as if you have POTS, the first things they start with usually are increasing fluids and salt intake, which usually is just salting everything you eat, I was never given an amount of salt. I was told to not worry about how much salt I had, which is usually the concern. Wearing compression garments helps with blood circulation, to minimize the pooling in legs and feet. The other thing that is usually added in from my experience, and talking with many others is a beta blocker.
With that being said, I ALWAYS tell ppl to follow your gut instinct. You have to be your own advocate, and of there's anything I've learned over the many years of my journey, it's that. If it were me in your shoes, I would get a second opinion. That's just my two cents, fwiw. Hope that helps.