Fludrocortisone and Midodrine are both medications that can help raise blood pressure. Ask your physician if one of these medications would be right for your situation. People are not generally prescribed medicine for low blood pressure, as it's not often a cause for concern unless it presents with symptoms.
Why do the middle fingers lock up when experiencing pain in neck and shoulders?   One cause could be some kind of impingement (pressure or swelling that applies pressure) of the spinal cord at C7, one of the cervical segments of your spine.
Boutonniere deformity, also called buttonhole deformity, can happen due to rheumatoid arthritis. The middle finger joint will bend toward the palm while the outer finger joint may bend opposite the palm. It may be the result of chronic inflammation of the finger's middle joint. Treatment may include splinting to keep the middle joint extended.