A couple of things: A recliner helps me a lot. But make sure it's one that encourages him to sit with a straight back. If he prefers his bed, he might like a wedge pillow. Either the long or short side can go on the mattress with the other side against the headboard, giving him two possible angles to try.
Maybe try one of these pillows. My family calls them “husbands” but I’m not sure if that’s what they’re technically called. Might be more comfortable than just regular pillows. The only other option I can think of would be a hospital bed where you can raise the head but that may be too expensive.
Get yourself a copy of this book, which takes an integrative approach to heart failure management. It stresses diet and exercise (obv) but this was the best resource I found addressing supplement stuff and other alternative therapies. (Cardiovascular function depends on the operational capacity of myocardial cells to generate the energy to expand and contract. Insufficient myocardial energy contributes significantly to CHF. Literally, heart failure is an "energy-starved heart.") CoQ10, L-carnitine, D-ribose, and magnesium have all shown considerable efficacy in treating HF.
I keep a spreadsheet of my weight, diet, exercise for the day, any medication changes, symptoms, etc. and it's probably the most important tool I have for identifying patterns in what's working and what's not.
I believe heart failure is reversible (structural improvement is called "reverse remodeling," btw) based on my own tracking of the results of my echocardiograms across several years (namely left atrial volume index enlargement and LV mass index), which I can cross reference with all sorts of other health data saved in my spreadsheet.
Working on stress management because it's very important but boy am I bad at it...
Not sure about the entrees to causing that. Is he on other meds? Sometimes entresto combined with other heart related meds can cause side effects.
As for low sodium, low potassium, I recommend you pick up this cookbook to start:
Roasting vegetables in coconut oil and herbs , baked chicken, 93% lean ground beef meatballs..
Lemon pepper seasoning is a great one to keep for flavor without salt. Eventually you won’t even miss salt because you notice how inflammatory it is.
Good luck!!!