Hypotension. Hypotension implies a decreased peripheral vascular resistance, decreased intravascular volume and/or inadequate cardiac force generation in systole. Normal pressure has adequate amounts of all these to result in a normal pressure range. Decrease in one or all contributes to hypotension.
Would love to. Would love to - but, in who? And with what underlying conditions?
Only if symptomatic. Only if it causes you to be dizzy or faint or if it unusual for you.
Not if you. Aren't having symptoms generally.
Symptomatic. It's too low if you have symptoms for example, there are people that walk around with blood pressure of 90/50 without any problems. There are others who are dizzy, wobbly and feel horrendous. Some of these general guidelines go out the window dealing with really sick people, intensive care etc. Different set of rules in that case.
Depends on the cause. Depends on cause rehydrate, replace electrolytes, stop BP lowering meds, treat sepsis, mi adrenal dysfunction etc.