issues setting up nginx as an https proxy

i'm trying to setup nginx to run as a proxy to aggregate multiple services. running on different ports on the server, using nginx to let me connect to all the services by going to a specific subdirectory. so i can keep only one port open in the router between my lab and the main house network.

i'm using the following config file from an example i found to do this, with a landing page to let me get to the other services:

        # Redirect HTTP to HTTPS
    return 301 https://$host$request_uri;

  

        ssl_certificate /certs/cert.pem;  # Path to your SSL certificate
    ssl_certificate_key /certs/key.pem;  # Path to your SSL certificate key

    location / {
        root /var/www/html;  # Path to the directory containing your HTML file
        index index.html;  # Default file to serve
    }


    location /transbt {
	#configuration for transmission
        proxy_pass http://10.89.0.3:9091/;  
	proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;$proxy_add_x_forwarded_for;
    }
  

but the problem i'm having is that, while nginx does redirect to transmission's login prompt just fine, after logging in it tries to redirect me to 10.0.0.114:1403/transmission/web instead of remaining in 10.0.0.114:1403/transbt and breaks the page. i've found a configuration file that should work, but it manually redirects each subdirectory transmission tries to use, and adds proxy_pass_header X-Transmission-Session-Id; which i'm not sure what's accomplishing: github gist

is there a way to do it without needing to declare it explicitly for each subdirectory? especially since i need to setup other services, and i doubt i'll find config files for those as well it's my first time setting up nginx, and i haven't been able to find anything to make it work.

Edit: I forgot to mention. The server is still inside of a nat. It's not reachable by the outside. The SSL certificate is self signed and it's just a piece of mind because a lot of things connect to the home net. And none of the services I plan to use only support http.