You are right when you say the points are grounded out through a coil in the flywheel stator.
To get a changed reading on your multi-meter when the points open remove both wires (coil and condenser) from the terminal on the points.
Fit a single cable of your own to the points terminal and thread this through one of the holes in the stator base plate and out from under the rim of the flywheel. Connect one cable of your multi-meter to this lead and the other lead to a good earth on the engine. With points closed there will be a circuit, with the points open there will be no circuit as indicated by your buzzer. An analogue meter with a moving needle gives a very good indication of the moment the points open, with the setting on ohms there will be a full swing of the needle when the points open.
I remove the flywheel first on my 349 to fit the replacement wire and to slacken the three stator clamping screws. Replace the flywheel and set the points gap. Check and set the timing. Remove the flywheel again, tighten the stator screws, remove your extra cable and refit the original cables. Replace the flywheel and tighten the nut to the required torque. Check the points gap again. it should not need adjusting.
To remove and tighten the flywheel nut I use a Sammy Miller steel band type flywheel holding tool. This holds the flywheel firmly without causing any damage. I have stators which have been ruined by trying to lock the flywheel with a screwdriver or similar through the points adjusting window, the proper holding tool is worth every penny.
Hope the above helps.