Yup, Safari on your pc could only show it because it was opened as a local file (because of the file:// prefix to the path). When using an ip adres Safari work like a regular webbrowser using the http- protocol. And there wasn’t a webserver on your pc to host it. So what you are looking for is installing a small webserver to host that index.html file as a mini-website. I can’t give suggestions as I’m out of the loop in these sort of apps. But I’m sure Google knows plenty of them.
p.s. Do you want to host this index.html page to the internet? Or do you only need to use it inside your home network? If the latter, then you do not need the portforwarding rules. But use the home network adres of your pc 192.168.0.105 instead.
Also, if it needs to be available on the internet, then you pc needs to be powered 24/7!
2nd also: (web)servers need to have a steady IP adress inside your home network. So either reserve this .105 ip adres in you router DHCP range for the MAC-adres of this pc. Or give your pc a static ip-adres in the network settings. Otherwise your pc might get a different ip-adres from your router after prolonged de-activation. Especially if it is a wireless connection, which is renewed on an hourly basis.