So the good news is that all this hard starting was at least done with new oil.
I would assume that Lasse also changed the Oil filter, So maybe Remove and drain the Filter and reuse? and just swap out the oil with some new.
LASSE: What type of oil did you use? Mineral or Synthetic? Not that it matters much from a contamination point of view as both types are diluted and compromised with solvents, but at least with a cheaper oil you won’t feel so bad disposing of 3.75 litres of 4 month old oil.
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What is suspicious to me is that the car had this issue during the ownership previous to Lasse. And that Lasse has NOT been using the fuel in the tank ( which should be drained and cleaned as that fuel would seem to be 15 y/o from the descriptions)
“When I bought it the guy said that the motor would stutter a bit when you try to start it with break cleaner, he couldn’t show that to me though because the distributor cap was broken. I did an oil change(on Christmas day, I just couldn’t wait 
) did some interior stuff and rebuilt the carburetor.
Now I’m trying to start it. I don’t have the fuel pump hooked up yet,”
So as the Distributor cap is now also replaced, and we have ether in the cylinders, Timing is the prime suspect.
I have seen the wires go back on incorrectly on replaced caps. You can get pretty much NOTHING ignition/combustion wise if you managed to get get the spark plugs firing on the exact WRONG moment like the top of the exhaust stroke. Not sure who that guy in my garage was that did that, but he did look a bit like me and was reprimanded.
A possibility that the previous owner may have had it mis-wired and Lasse replaced wires 1 for 1 when installing the new Cap, or that the Previous owner really screwed up the timing trying to get it to start on old gas and brake cleaner, and maybe damaged the cap or cap retaining clips in the attempt, as he states the previous owner was having trouble and the cap was broken.
Anecdotally, when I worked on Aircraft we were required to have the manual next to us, and open to the correct page, not that we always did, but a good lesson to that guy in my garage who messed up my spark plug wires. After years you just run on autopilot and sometimes guess at the Wrong #1 cap socket and then place the remaining wires in the correct order but wrong direction.
LASSE; also make sure that the Clips that secure the Cap to the distributor Body and in good shape and secure the cap and body correctly. If the cap moves it WILL colide with the Rotor and WILL punch a hole in the side of the cap, and damage the rotor. Possibly damage the clips further. Check the screws that hold the clips to the distributor body are tight Also there may be a little play where you can loosen the screw, move the clip down a fraction and then retighten in the case that the clip is not holding snugly. check page 53 fig 109 (Sure, now, the manual is next to me and open at the correct page)