Ok. So far I believe I fixed HTTP to work together with HTTPS access.
I was blind for small details. I had forgotten to amend proxy_pass parameter on nginx config file.
#proxy_pass http://127.0.0.1:8040;
proxy_pass http://206.192.23.166:8040;
Although, I still reluctant to accept the usage of external IP instead of local (127.0.0.1) within nginx configuration's file as well as aolserver's config.tcl.
But anyway, at least it works now I can't deny that.