..."I got 3.5 oz of seed from 4 brightleaf plants but now growing other varieties , I see that my original had huge seedheads unlike some of the other varieties I am now growing."...
There is a HUGE difference in seed production from one type to another. I have gotten as little as 100 grams, to as much as 3 lbs of seed from grow outs of 36 plants. (btw, Does anyone need a pound or two of Little Dutch seed? I'll make you a real deal)
..." should I let the seed air dry a couple months before I seal them in my ammo box with desiccant? "...
We let the pods ripen on the plant until they are brown. On some varieties they ripen fairly evenly and don't start spitting open as soon as they are dry, and we can clip the whole head at once when it's all matured. Others require snipping out the earlier maturing brown pods as they dry because they split open and start dumping their seed. Those types are a pain because they require multiple pickings and rebagging each time.
All the picked pods and cut flower heads go into an 18 gal plastic tote after trimming off any leaves and as much stem as possible. The totes get stacked out in a rack in the sun to finish drying completely for another couple weeks. Once everything is crunchy dry it gets put into our home made thresher, which is basically a modified version of a garbage can sunflower seed thresher I saw on line. Ours is a kinder and gentler version than the sunflower thresher though. Basically it uses spinning rubber tubing to break up the pods and flower heads without pounding the seed into flour. It works well for several things we grow. Once everything is broken up it goes into a sifter bucket with window screen in the bottom. A couple passes through it removes all the big chaff and bits of stem. Next everything goes through a #600 sifter screen and finally into a #400 screen. The #600 catches more chaff but lets tobacco seed fall through. The #400 lets fine chaff and immature seed fall through and catches all the good tobacco seed. The rest of the chaff in the seed must be removed by winnowing.
Once the seed is cleaned we put it into 1 gallon zip lock backs. We DO NOT close the bags. We put them into boxes and move them to a nice safe dry room indoors where they sit propped open to continue airing out for another month or more. The moisture content needs to be down to around 10% before sealing them up. You want 7-8% if you're going to freeze them. I once made the mistake of sealing up some seeds in a glass jar right after threshing that I thought were dry enough. A couple months later the jar was lined with white fuzzy mold. I did the same thing with some pods I was saving by sealing them in a zip lock bag. We haven't had any problems since we started letting the bags breath for a while before sealing them.