Hi @anon8932282,
Giving a straight answer is almost impossible. Indeed, beeing stealthy not relies entirely to your proxies setup, your machine must be hardened too in order to avoid network fingerprinting, etc.
The best tip that I can give you is to setup a VPS then ask, to your provider, for a pentesting authorization. This will allow you to conduct aggressive scan forward your target from a legal manner. It is surely the best way to improve your knowledge as well as figure out your issue.
P.S: Keep in mind that a lot of tools such as Nmap is not reliable behind proxies, triggering falsing and by consequence skewing your recon.
Hope it helps.
Best,
Nitrax