Yes going to 300mg BID in a patient with normal renal function, no other sedating medications (no benzos/opiates/other garbage) would be reasonable for neuropathic pain. Max dose gabapentin (1200mg TID or 900mg QID) also is reasonable. Gabapentin prn makes no sense. Long term combining gabapentin and lyrica makes no sense, but short term cross titration is reasonable when switching one to the other at high doses.
In terms of indications especially at high doses- I leave 'fibromyalgia' up to PCP/pain/rheumatologist as it is not a neurologic problem that I am going to manage. I would primarily use it for clear neuropathic pain (small fiber neuropathy (most commonly diabetic obvs), chronic painful mononeuropathy such as a old traumatic lesion, radiculopathy, post herpetic neuralgia, TG/atypical facial pain). I use it only after cymbalta and gabapentin at high doses didn't help and people already tried topical creams if appropriate. I wouldn't recommend it for 'back pain' or 'neck pain' that is not clearly radicular.