[nginx settings] How do I combine a proxy pass: unix with a TCP:Port options?

Hello.
I have an Ubuntu 18.04 with VestaCP
(A Lightweight Web Hosting Control Panel which is simple and does exactly what I want to do with a few simple clicks)
for Hosting my Python Apps using Gunicorn.

I have configured Gunicorn to use a unix socket for more speed/performance and when I use that socket on my nginx settings file, I cannot use other options or I do not know how to use/combine them with proxy_pass unix socket.

VestaCP provides me customized settings for my web-apps for they are not customized for unix sockets
The reason I want to combine those settings with unix socket I can do my job a lot easier for customized error documents


When I don't use proxy_pass, an example of 404 Error:
https://i.imgur.com/1KG3UE2.png

If I use proxy_pass with Unix socket I get this:
https://i.imgur.com/a9ahcxF.png

and my settings
https://pastebin.com/26G6bT27