I'll throw in my .02 and that's twice what my advice is worth.

In my entire life, I've NEVER seen an application where a vacuum secondary carb is called for. I know some carb Giants and gurus like David Vizard leg hump those carbs to death, but I've used enough of them in real life to know its a [censored] to make the secondary side happy. In fact, I've been on the dyno several times with decent street/strip stuff that at 7000 didn't pull the secondaries all the way open. Just worthless. A double pumper is more tuneable than a VS will ever be. The fallacy that you can run a bigger VS carb is complete horse crap. 99% of the time, you operate on the primary side, so how did the VS help?

That said, you have to work with what you have, or buy a better carb.

I'd start over and unhook the O2 sensor. Then I'd tune the big out of it and make it run. Then put the O2 back on and tune from there.

I'm going to say that the best money you'll ever spend (unless you enjoy working on stuff just to say you did it) will be spent send the carb to someone like Thumprdart or Mark Whitener and let them help you. It will be cheaper and quicker in the long run.

FWIW, I trust my ability to read a plug long before I trust any sensor. But I'm very comfortable reading plug. I'd make it run first and then tune it. The O2 isn't perfect, and can screw you.

For all the screaming and whining I hear about no two flow benches or dynos read the same, why would anyone think that every O2 sensor reads the same? Is it leak free? Is it mounted the same? Who knows?

Make it run and then tune it. And where it runs the best is the numbers you use for your O2 sensor. Timing lights read differently. And whatever you do, don't flow Holley jets. You'll see what production tolerances look like.

Don't get caught up in sensor numbers until the car performs.