What did I do? Help?

BTW, where the slot in the distributor drive is, makes not one bit of difference, except only one position is factory correct.
The only thing that makes a difference is where the rotor is pointing when;
A) the points open, or
B) the reluctor triggers.......
in relation to where the tower is, when the spark occurs.

You can take that distributor out, rotate the drive to any of it's many positions, and you will always find a tower to synchronize to. Whatever tower the rotor points to, if #1 was at TDC Compression, that new tower will be number one; you got eight choices.
Having said that, the factory position will get you the best fit for the custom length wire-kits.

However, when determining the distributor clocking AFTER the 10 degrees has been set;
you gotta lock the Distributor down, when the coil fires. That means with the key on and the coil wire near-grounded, you gotta rotate the D, contra-rotation until you get a spark, then verify that the Vacuum advance unit is in a good spot, then continue.
Contra rotation means starting with the Vcan banged up against the firewall, pull on it until you get a spark, then STOP.
Then mark the D as to where the rotor is pointing, then install the cap AND verify the mark you made is very near the center of a tower ; then choose that tower to be your number one.
If you do this very carefully, and your marks on the balancer are correct, you can bet money that your idle-timing will be nearly exactly what you set the balancer to. If it is not, then either;
1) the flyweights were not properly parked at the outset, or
2) the springs are too weak to keep the advance mechanism from moving, at idle.
3) or the ECU is altering the signal.

BTW
if the rotor is not under the center of a tower at 10degrees BTDC, and you cannot force it to go there, and it is in the CW direction PAST the tower, then your dizzy is either incorrectly assembled, or it is crap and will have to come apart to be reindexed.
IF YOU TOOK OFF the reluctor, you may have reinstalled it wrong, so Check the top of your reluctor and find two arrows one above each milled roll-pin slot. If your D rotates CW as it does with SBMs then you should be on the slot that points ">" (which is CW). This is supposed to put the rotor in the right place, after the trigger fires.
If you still can't get the rotor more or less centered under a tower, then you are gonna have to either;
A) re-index it, as it has been welded together wrong. or
B) just file a new slot on the cap, a few degrees over so that the clips still fit, or
C) just move the tip of the rotor over......... which is the easiest. and they make rotors with adjustable tips, just for that.

BTW,
From my desired total advance, I subtract half the mechanical advance, to get the balancer base position. For instance; if my Mechanical flyweight advance is 20 degrees, then 34 less half of 20, equals 24 and that is the number that I will set the balancer to, and then I set my rotor to directly under a tower. In that way, the advance will march 10* towards the tower on the first half of advancing, and then 10* past the tower, on the second half.. At least that is what I'm hoping for. In that way the rotor is never more than 10 degrees from the center of a tower; which is never closer than 50* to the next tower. This is real important with a high-powered coil like the Super-coil, lol.
But recall that the base position starts with the distributor rotating, until the coil fires; and the VA ending up in a useable position, off the firewall, and not jammed under the carb. If the VA ends up in a bad place, remember, I said it does not matter where the Oil-Pump drive is, no other position will make it better!, so don't go moving it just to find out I was right. I've been down that road. If the VA is in a bad spot, it's because the Distributor is poorly synchronized, and will have to come apart, or something else will need to be moved.


BTW
where all the working parts are, inside the D, depends on the arm of the VA actually anchoring the "breaker-plate". If the arm falls down, then the "breaker plate" will float around. I imagine it will eventually find a stopping point, but who can say what the advance will be, except to say, not where it's supposed to be, lol
Happy hotrodding.