Disconnect the rubber line and see if the metal line from the boot (trunk) is clear, first.
If it is, then ditch the rest in the engine bay and the rubber line going to it, if your egulations allow.
There is another rochester valve in the engine bay gubbins too.

 

What I did for these 3 tank vent pipes/tank venting was link together 2 of the vent pipes, block off the 3rd.
This new single vent pipe then loops up into the buttress as high up as possible, then back down, through a cheap inline plastic fuel filter located near the ECU, & out the bottom of the car.
My theory being that looping it up then back down will minimise the chances of liquid fuel coming through it.
In terms of venting the tank it seems to work well - no issues with tank pressurisation or when filling up.

It didn't work for the smell mind, I still have the fuel smell when I open the boot Pretty sure I have the tiniest of leaks around one of the fittings, or perhaps fuel permeation through some of the old hoses I haven't replaced.

I'm interested in your question about where those 3 tank fittings go inside the tank, whether it's safe to block all but one up (which one?) & whether there is any pipework internal to the tank that routes them to the other end or elsewhere.

 

Thanks- Mine was a metal line all the way to the canister. I disconnected it- and could blow air thru it. So I pulled the canister and tossed it. AND the 4(!!) vacuum lines going to it. All are plugged off.

Will be hooking up battery and seeing how it runs.

 

Absolutely the best thing to do.