I have 15 btdc initial. It's plugged into ported vacuum (above the throttle plate)

This stupid vacuum pot when plugged in was pulling 10, so a total at idle of 25 btdc. Backed off the pots timing with the allen head adjuster, got it to about 20 btdc at idle with the vacuum pot in.

I haven't messed with any mechanical advance because, these guys at Wysco don't wanna talk to me at all. They send me to their dealers, who don't seem to care now that I already paid for the damn thing. So i don't know where to get weights/springs for it.

Its a 73 dart, a stock 1967 273, 904 trans, on 2.96 gears. Dual exhaust, no power brakes.

When i had my /6, which had a carter BBD, i idled the thing down until my ported vacuum didn't pull any vacuum. Then i set my initial timing, when i pluged my V.A. in, my timing didn't change at all. It wasn't until I was at partial throttle.

Two things odd about your results.

The 3/32 hex key in the vacuum pot should only adjust the amount of vacuum it takes to move the pot. The number of degree it moves with vacuum, compared to without vacuum is a fixed into a stop on the arm. Not adjustable (unless you modify it).

If you are using ported. You should not have vacuum at idle. So your timing should not change at idle with or without the connection plugged in at idle.

15 initial is pretty good. A 2.96 geared 273 is not going to do too much off the line.
Switching the vacuum connection to manifold vacuum will give you a slight increase in torque at partial throttle because you will have more timing but deep throttle will be the same.

15 initial(checked with vac plugged) sounds good, ported(in this case) vac adv sounds good, If your total is 35(or close to it) checked w vac plugged you're good. I think if you could get your idle speed down to where you have no vac(to the vac adv) that would fix most of this issue. The mechanical curve(springs/slot length) & the vac pot amt of adv could fine tuned later. I think you need to get those throttle plates closed further rather than backing off the amt of vac adv.

Yea i think you're right about closing the throttle plates.

In regards to the vacuum pot, when i adjusted the diaphram via allen key, i think thought it made it where more vacuum was required, since the vacuum rate at idle has been constant, that would change how much advance right?

I think part of my issue, is the weather has been going from like 20-55 degrees within a day and it makes it almost impossible to get the air/fuel mixture set to adjust idle.

Adjusting the allen key in the vacuum pot changes the preload on the spring that wants to force the arm back to the zero advance position.

Once the vacuum level is above the preload the rate (degrees per "Hg) remains the same.

So, increasing the preload will increase the amount of vacuum required to get the advance to start moving and ultimately the amount of vacuum required to get full stroke from the pot.