Can predinose help w/dizziness r/t autonomic def? I drink fluids, salt doesn't help low bp. 10 mg predni helps m. I also have connect tisss disease.

Yes. Prednisone helps with some types of dizziness and many autoimmune diseases. Chronic steroid use has risks, so be sure to work with your doctor on this.
Glucocorticoid. Prednisone has mainly glucocorticoid activity (used to treat inflammation) and not much mineralcorticoid activity (used to increase fluid retention), compared to other steroids. But definitely one of the side effects can be fluid retention and increased blood pressure, it is much less helpful for autonomic dysfunction than Florinef (fludrocortisone) (mineralcorticoid) and Hydrocortisone (mineral- and glucocorticoid.