I checked [with my real IP and I've already repeated the first two steps that I've listed before] and it gave an error [on bitnode is still unreachable].
If you're running through a VPN, then you should check with your VPN. Are there any steps to enable portforwarding using your VPN? If canyouseeme.org shows false, then the problem is with your portforwarding and not Core.
I believe that means disabling it
["=0"] and it appears that it has something to do with Tor users using it, am I right? I'm using the default settings and judging by @
nc50lc's comment, it seems there's no need for me to add it.
Yup. The setting is only disabled if you're running a proxy or through Tor. I was asking that on the premise that you might have specified that, given that it is turned on by default.
CMIIW: If I continue to run it in its current state, I'm still contributing by verifying and connecting to others while other nodes just can't connect to me. Am I right?
This is correct. It is good to be able to have inbound connection, for the network but it doesn't necessarily mean that you're not contributing to the network. Even if you do enable inbound connection, then the primary benefits should fall on you and the overall benefits on the network is secondary.