Reverse Proxy Expert for Embedding External Slot Game via iframe (Node.js / WebSocket)

I'm embedding a slot game from an external provider into a casino domain using an <iframe>.
I already have the local assets and all captured headers (including WebSocket and launch parameters).

I need a specialist to help set up a complete reverse proxy that does the following:

✅ Serve static local files
✅ Proxy WebSocket connections properly
✅ Spoof the origin and necessary headers
✅ Rewrite paths if needed to avoid 404/403 asset errors
✅ Ensure the game loads and runs correctly in the new domain

? Requirements:
Experience with Node.js, Express, and http-proxy-middleware

Deep understanding of WebSocket traffic and spoofing techniques

Ability to debug and resolve missing asset errors (404/403)

(Bonus) Experience with casino platforms or game integrations

? What I already have:
All local game files downloaded

Captured headers and params (including WebSocket URLs and session tokens)

Basic server running (Node.js + Express)

Proxy partially working, but missing adjustments to fully spoof and resolve errors

? Please include past relevant work or explain your experience with reverse proxies and WebSocket spoofing.