Can fibromyalgia be fatal?

No. Fibromyalgia is a chronic condition that can be challenging to treat, but it is not fatal.
Not directly. Not directly & organs continue balanced function. Major depression oft evolves &, combined w. severe pain, can potentially arouse suicidal ideations. Opiates officially discouraged for FM; based on authority of "hyperalgesia", an unproven theoretical concept. Pain control of FM patients oft problematic & ineffective. Suicide acts unfortunately unstudied.
No. As far as we know, no. In fact it is not felt to shorten lifespan at all. However it is a painful condition with a variety of manifestations. Its severity can range from mild where people lead completely normal lives to severe where people are significantly disabled.