If your engine is like my 1200, the hole is low on the right side of the block. Look for a pipe plug, most would lead to an oil line.

Filler is ok until the car gets bumped, it just is not stong in impact. So if you want to have handles again, you only need to hit it in the right spot and then you can put the handles right back in the holes.

There are ways of making the filler stay put:

1.best: welding a patch over the hole. Complete the work with body filler.

2. almost as good: Rivit a patch over the hole and finish with filler. Riviting is easier, takes less equipment and heat can burn paint or distort sheet metal.

3. less good: tack weld one or two lengths of welding rod across the low spot and then use filler. The filler will be locked in place but can still crack slightly at the edges.

4. you could run small screws into the depression to give the filler something to cling to, but they can't stick up much or it will be a disaster.

5 alternatively, you can drill a couple holes through the dimple for the filler to flow through and secure itself. Has the advantage in shallow depressions as holes can't stick up through the filler ruining the job

That is a common value and should work for ordinary point & coil ignition. (at least for a while, because if the value is off the points will erode).
I've only used single wire condensers in point and coil ignition systems in my early 70's datsun engines.

A two wire one could be a single case containing two condensers back to back. This is a non-polar capacitor(or condenser), most common in speaker crossover circuits.

I have not seen them used in ordinary points and coil ignition. but I've seen two wire condensers mentioned on this site so I'd do a search for that to see the reason for them. What year is your car or sort of ignition system is in our car? Datsun was transitioning away from points and coil(Kettering ignition) in the mid-70's.

Condensers are so inexpensive, I'd get the right one for your car

The movement that you noted would seem to be due to a slightly loose fit between the distributor body and the block.
You could use shimming to reduce that play.
I have used aluminum foil for very thin shims and beer can metal for somewhat thicker ones. You can easily buy shim stock, I usually buy mine from model building shops.

Nicely written John, motor oil seem to floats away the abrasive debris very well so I also wipe with it.

In general, I try not to change cam bearings unless really needed.

torque and power? Sounds like a need for some boost pressure.

If one carb floods and the other does not flood then everything but carburetor trouble is eliminated.
The throttle body, and passages can not cause this sort of trouble ( not unless there is a crack in the float bowl) so all that is left is the float and the float valve.

You are doing things mostly right but it certainly is frustrating.

There are a few more things which can cause trouble but I'm thinking it may have something to do with the distributor.

1. check for continuity of the small wire between the points and the coil. It should have less than an ohm resistance.
After checking it wiggle it a little and check again.

2. The advance mechanism in many distributors is controlled by fine springs which resist the pull of spinning weights. Things get strange if a spring breaks.

3. It is far less trouble to check the ignition timing than to take the distributor apart. You have to adjust the timing in any case as you worked with the points. Check the timing.
It is also under vacuum control and that hose should be squeezed shut when testing timing or the numbers will be way off.

Electrical problems are usually on or off,but sometimes they be intermittent.

The 30 second runs do sould like a fuel-related issue as they repeat so evenly. It can run a little while on a floatbowl of fuel, but not very long.

Valve timing chains can jump and make an engine stop, but they usually don't change back and forth so the engine runs and stops again and again.

An anti-dieseling solenoid is supposed to shut it off.
So if it was acting up it would be a prime suspect. If there is one there, remove it, remove its "pin" and replace the solenoid valve.

For the short time it runs, does it run normally?

Persist. You will solve it.

If the problem took place suddenly and changing the points helped. It is electrical. The 30 second run is possibly a different problem. Is fuel getting into the carb? Check the little window in the carb , it should be right to the center.

the needle can simply be wiped clean with your finger. The seat for the needle requires something smaller. you might invest $2 for carburetor cleaner in a pressurised can. that way you don't need air to blow out the passages etc. If the float is touching the side of the float bowl the carb will flood. Plastic floats dissolve in gas containing ethanol. Metal floats develop tiny leaks, fill with gas and sink but they resist ethanol fuel better than the plastic ones. I'd put a new float in the carb. as they are not expensive and it may help. Be sure to adjust it so thefuel level is in the middle of the little float bowl window.