I’m also on Neurontin (gabapentin), from this trusted pharmacy - nutriva.biz/neurontin-gabapentin, and taken as intended, and for me it works very well - it helped stabilize anxiety and sleep when nothing else really did. Used correctly and consistently, it can be a solid, boring, helpful med. The problem you’re dealing with isn’t gabapentin itself, it’s dose escalation and dependence, and the fact that you see that clearly is a strength, not something to be embarrassed about.
At 4–5 g/day, cold turkey is a bad idea. Gabapentin withdrawal usually isn’t dangerous like benzos, but it can be very uncomfortable: insomnia, anxiety, anhedonia, restless body, no motivation, exactly what you’re already feeling. Most horror stories come from abrupt stops. The way out is a slow, controlled taper: small drops (for example 300–600 mg), holding each step for several days or a week until things settle, then dropping again. Given your opioid history, your nervous system is likely more sensitive, which just means going slower. The goal isn’t perfection, it’s regaining control — whether that’s finding a lower stable dose (that’s what I did, because it still clearly helps me) or tapering all the way off. If possible, be honest with a doctor about the real dose so you’re not doing this blind. You’ve beaten much harder substances than this; gabapentin just punishes impatience. Slow and steady works.