Budget advice: 14 months in Asia

My partner and I are leaving in February for (hopefully) 14 months traveling through Asia. The below is our rough initial itinerary, but we’re very open to it changing as we go! We are hoping to budget $500 USD a week ($75/day) total for both of us. Is this achievable? We’ll be staying in hostels, eating street food, not against cooking sometimes, and hopefully only traveling overland and avoiding air travel. Yes… we know we’re in for lots of hours on buses and trains! Keen to hear thoughts and advice from any seasoned travelers out there!!

Feb - Sri Lanka Mar/Apr - India May - Nepal June - India July - Pakistan/China Aug - China Sept - Vietnam Oct - Laos Nov - Thailand Dec - Cambodia/Thailand Jan - Malaysia Feb/March- Indonesia