You are going to have to fix that.
Alternately you can accurately find TDC and make a new mark on the balancer or front cover.
As for not happening without a load.
If the timing is anywhere close it will run without a load but load up the engine and then the timing needs to be correct.
Have you checked to see if the vacuum advance is working? When you hooked it up to manifold vacuume the advance should have gone up and the rpm should have gone up significantly
