Wow! What a holiday treat!

I hope it's not snowing where ever you are because you are in the thick of it now!
That's bad news to find out a "strong dim wit" had a hold of a wrench or worse that another "heavy fingered dim wit" used an impact driver as a torque wrench.

It is hard for me to imagine the camshaft bolt ever getting that tight without snapping the bolt.
An air ratchet driver can reach 35 foot pounds pretty easily!
I surely hope it didn't get stripped in by the impact driver dude!

Have you tried loosening the intermediate sprocket bolt that drives the distributor around!
I think it has the same size diameter bolt in it.
It has been a long time since I have had to change seals or a water pump on any of my six Volvos so the sizes are vague.

How are you locking up the camshaft, so it cannot wiggle. If you are trying to hit that "sweet spot" to knock the bolt loose, everything has to be ridgid.
The wrench and hammer usage requires nothing to bounce or flex about.

I personally like a lead hammer and mine is has solid lead head.
There was a lead hammer service where I worked in the seventies that provided them to us. Today, I just melt lead more into a mold around the old handle that I kept up with for years.
Nowadays, because OHSA banned the use of lead in so many ways, they sell lead shot inside a container, inside a molded plastic or rubber head.
They call them "dead blow" hammers and work fairly well when you want to set a part in a vise without marring it. Otherwise, they are a bit light on hitting dead solid and passing on mass force!
A heavy solid weight can really move things but, you better use it carefully.

To explain the bit about rotating the flats, I can give you an example of where that come from.

Back in 1982, I was hired temporarily for three months, due to a layoff period from my previous company, to overhaul a steam turbine that drove a dynamo for the Edison power company in Long Beach, Ca.
There we removed three inch diameter, through studs, that were about four to five feet long from the steam turbine casings.
That required "slugging wrenches" to turn five inch-plus diameter nuts.
On those, it was all about using 20 pound steel sledgehammers and swinging between the feet to hit a super thick handle.
We moved the nuts loose a flat or so and then use big impact drivers to move them rest of the way loose.
When we put them back in after the rebuild we use that same 1 &1/2" square drive air driven impact wrenches to set the studs. Nicknamed, "Big Bertha!"

These studs had a long blind hole down in the middle, that we measured to the bottom of with depth micrometers, before the first tightening routine.
After using the impacts as much as they would turn them, we took new measurements.
This was to tell us how much we stretched them.
Those measurements were sent up to engineers someplace so they could tell us how much more of a turn of the nut was needed to get the stretch or torque needed on the stud. It would come back to us as degrees of more rotation.

It was then that we inserted some heating rods down inside those holes.
They were like a long heating element that you have in your home oven but made straight.

Once the studs heated up, we took our wrenches and beat the nuts farther around and let them cool. Then one more measurement, to confirm the stretch!
Usually it came out, right on or within a tolerance. The pitch of the thread in the nuts or stud threads are a finite distance of a helix.
This was Very important stuff considering the use of super heated or high pressure steam will heat those heavy cases up!

This also was the second time in my career that I got to use what is called the "tight wire" method of aligning end bores of a machined housing. Or in this case, placing several plain bearings true to each other over a long length.

It's There, I learned about "oil stacking." I was not a machinist mate in the Navy but a Machinery Repairman that made shaft bearing for ships but never set one!
It's where oil stacks up on one side of a rotating shaft while inside the bearing!
This is due to friction and gravity!
We also used an offset dimension to shim the bearings around in the housing, in relation to the turbine fins place to run in.
The turbine actually lifts up and stays up on a "pumped in" bath or film of oil.
The oil tanks nearby are the size of a small house.
The first part of my new job was wiping them down inside until spotless.
Almost like cleaning bilges of an engine room in the Navy!
Oh, what a young man I used to be!
But being a Navy veteran has had its pay backs over the years with decent paying jobs that companies are truly in demand for skills and work ethics.

On start up, The turbine is "jacked" around slowly from the outside until all is hot from some steam throttling before going up to speed. The mechanism is called a jacking gear, of course!
When up to speed, the bearings oil is not the same thickness all the way around but the turbine shaft comes up running it is true to the thing called a "pickle."
This is the "slang term" used on the turbine deck by a crew call "steam division animals."
The reason I learned that they earn that name traveling from one work site to another.
Anyway, It's the rotor inside of the generator.
It just so happens, I was a thin enough person back then, that I got the pleasure to lay inside of of that Dynamo.
They needed to install steel belly bands in between the outer housing and around the outside of the windings inside! You were first asked, "Are you claustrophobic?"
It was a GE modification to reduce humming of the windings or coils. If they move around more than they should the wires can wear against each other.
Doesn't sound good when they used hydrogen as a cooling medium. It removes about as much heat as water does per pound I found out later.
That same year the Redondo Beach unit blew its end bell off or cracked it. I overheard that anyways. Then there is badges, for those who get to work overtime, to glow in the dark at nuclear places? Steam division!


In your case with the crankshaft, the 44 foot pounds is preliminary set, that's within most everyone's tool box torque wrench.
The 60 degrees is really only one flat of the hex head as they are 60 degrees each. 360 degrees divided by 6 flats is 60 each!

You mark one to the pulley face and move the bolt one whole flat from that line. I believe and it's a guess, that it probably works out around 120 foot pounds OR about all that an electric or 100 lb. air power impact wrench can hit!
For me that's plenty tight.
I don't know what forces they are trying to overcome that they think will ever loosen that bolt but an impact one .... From where on a rotating shaft!
Harmonics has more to do with the flexing of the whole crankshaft with stroke pluses at certain speeds and loads. This is a four banger with five mains ... I don't get the worry, but then I'm not an engine maker!
The early red blocks never had a damper so the cranks might be thinner or lighter over time?

All I can advise it get everything setup without hardly any play on that bolt in your wrench setup.
A six point socket is the first way to go and you have the whereabouts to know that already.
So it comes down to mass rules!

The oil drain plug is normally a 3/4 inch by 10 pitch thread. The same as the thread inside the spin-on oil filter thread. I think I screwed a drain plug into one once to check that out.
That 15 mm must be a down sized oil plug arrangement because 3/4" is more like 19 mm.

Good luck to you during the holidays!

Phil