Piriformis syndrome and sciatic nerve treatment, do you have any recommendations?

Stretch injury. If your piriformis pain is secondary to pelvic imbalance and it's constantly stretched, the last thing you want to do is stretch your piriformis. It will aggravate even if it feels good stretching it at the time. Find a physical therapist who can do myofascial release or facilitated positional release and teach you relaxing exercises.
Treatment. Gentle exercises can help a lot with piriformis syndrome pain as can icing the areas near the muscle. For sciatic nerve pain there are medications like Gabapentin that help some and watch for positions that cause you pain and try to avoid these positions. Some manipulation from your doctor might help.