Orthostatic hypotension

Back again with several new questions based on the observation by my brother that a number of my current complaints sound as if they are related to orthostatic hypotension.
Background:
Diagnosed about September 2022 with inoperable pancreatic adenocarcinoma (then aged 73), since then I've developed "chemo feet" and balance issues which I have passed off as originating in spending too much time lying down. On weekends following a Chemotherapy infusion (Abraxane & Gemcitabine) I become more aware of lightheadedness, often occurring when I first stand up from lying around "taking it easy" to recover, or standing up after sitting up to eat in a chair that fits me properly.

After reading this review from a reputable source
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2888469/

I have several questions that I'd welcome comments related to the following
(1) are some of the symptoms I'm currently attributing to "chemo feet" caused by orthostatic hypotension? if so, does that advance the cause at all, in determining appropriate therapy?
(2) hydration: there is little doubt in my mind that I'm not getting enough fluids on board, although I do agree that in a normal person (and have to add now, I think, younger) individual, thirst is most likely an adequate guide to drinking enough
(3) Can potassium replace sodium? given that my current oncologist would like me to reduce my sodium intake (I do not typically add salt except to a daily meal of organic mixed veggies which does need some "salt" to bring out the flavor; I've recently switched to a commercial blend of half sodium and half potassium - don't remember the name of the product purchased by my husband). IIRC this is to address what my doc has assessed as venous insufficiency affecting my left leg where I have an old pinned fracture of the ankle; I don't particularly notice anything similar with my right leg where what is obvious is wasting of muscles and subcutaneous tissues
(4) I've been propping my feet up at night, again (IIRC) to address the supposed venous insufficiency happening in my left leg, when maybe I should be propping up my head. Since I've never really been comfortable sleeping on my back and have slept on my side as long as I remember, should I still be elevating my head?

Possibly this question belongs in a different group.