Whether or not your motor wants vacuum advance will depend on the compression ratio, quality of the gas, the shape of the combustion chamber, and a whole bunch of other variables.Generally speaking, the sooner you can ignite the fuel air mixture and not cause detonation, the more efficient the motor will be and the more power it will make. Vacuum advance really becomes advantageous at crusing speeds, steady state running at highway speeds where additional advance over mechanical advance amounts can gain more fuel economy. Learning how to tune your advance curve for your motor takes time. It sounds like you are 1/2 way there, with learning how to limit total mechanical advance and changing springs and such, and if you can grasp the concepts around tuning mechanical advance you can grasp tuning vacuum advance. Whether your engine wants or likes it can only be determined by trial and error, and a lot of testing.

This is separate to your vacuum advance questions but I need to ask - Lumpy cams and T Quads do not mix well in a stock configuration. I have to ask how the idle quality is. The metering rod set up in a TQ is controlled by engine vacuum, and if you do not have sufficient at idle to pull the metering rod piston down against the spring, the metering rods will dance up and down, doing a real number on the idle mixture, richening and leaning with every vacuum pulse. This can happen in a Holley too, when the vacuum is lower than the power valve setting, allowing it to open at idle and causing the car to run real rich. The solution in a Holley is to put in a power valve with a lower vacuum opening setting - on a TQ the solution is to clip 1/2 a coil at a time off the power piston spring and reinstall it and watch it at idle, stop clipping coils when the vacuum can keep the rods down at idle.. YMMV...