Preheat oven to 400°F. Halve and seed the spaghetti squash, lightly oil the cut surfaces, and roast cut-side down for 35–40 minutes. Scrape into strands and blot away excess moisture.
Whisk fish sauce, tamarind paste, tamari, lime juice, sweetener, and red pepper flakes together.
Heat oil in a large skillet over medium-high heat. Cook chicken for 4–5 minutes, until it reaches 165°F; remove. Scramble eggs, then cook garlic, green onion whites, and bell pepper for 2 minutes.
Return chicken to the skillet. Add squash and sauce and toss for 2–3 minutes. Fold in bean sprouts and half the peanuts for 30–60 seconds. Serve with remaining peanuts, green onions, and lime.