So if I were to use this, at verbatim, I could still access my local network resources just fine - but would have no unternet, unless I started clash with that tproxy configuration?

And, since my router has three ports (wan, lan1, lan2), how can I make this work network-wide? lan1 and lan2 is where my pc and wifi AP is connected to, whilst wan goes into the modem for PPPoE.