total timing reading accurate with no load?

No load is the normal way of checking as it relies on RPM's.
Fine tuning the vacuum advance is done under a load because vacuum varies under load due to throttle opening.
Vacuum advance tuning is done more by ear while driving the car.

The problem you are having is as thesiren74 says, that you need to limit your total mechanical timing.
The reason is that the factory advance setting is usually 0 degrees or TDC and the distributor is made so that 0 degrees the advance should be close on the total.
When running more initial the distributor lets your timing go well over the recommended total.
Hope this explains things clearer.

The limit plate from FBO (4secondsflat.com) has selectable slots that limit the distributors advance weights and therefore limiting the total advance the distributor can throw in as your RPMs increase.
I have used these extensively in building performance distributors for Mopars.

You might also check into the performance advance spring kit while you have the distributor open anyway.
This kit allows the advance to come in sooner than your 3k by using one spring in the kit to replace the heavier of the two springs in it now.
Your total should be all in around 2.5k with this spring installed.

Mr. Gasket Distributor Advance Kits 925B here:
Mr. Gasket Distributor Advance Kits 925B

Here is the address for the limit plate:
How to limit mechanical advance in a mopar distributor, tuning for street, strip or all out racing, cure that rich stinky idle, win races

If you have a Paypal account you can send $22 to [email protected] with your shipping info for a J685 Mopar limit plate.
Or just call Don at 541-942-5920 and get one that way.