How do I keep myself from fainting due to low blood pressure? I'm 292lbs so I try to avoid salt at all costs.

Perhaps too low salt. You don't have to severely restrict salt intake unless you have water retention from heart problems. If it is okay with your doctor, increase your salt intake modestly to see if you can avoid fainting spells. Wearing support stockings or an abdominal binder may also help.
Keep hydrated. The weight does not require you to reduce salt -- yes, you need to work with your doctor about the weight management, but you need to keep hydrated and the regular salt intake will keep your blood volume necessary for normal organ perfusion (especially the brain) -.