mama bear stove pipe conneciton

Older stoves used 6 inch OD pipe for the outlet, newer stoves use 6 inch ID. So yours will measure the wall thickness smaller than 6 inch. If you have a hand pipe crimper, overcrimp the end smaller to fit. It's not a big deal to slip it over the stove connector since it would only drip any condensate formed in your pipe back down. The chimney flue is the area that would drop below 250* causing condensing of water vapor. So it becomes more critical in a flue that would drain all the way down from the top and leak out. You're going to stay well above that temp in your pipe leading back to the stove.

Here's a case where the flue could drain back to the stove, so I use a T preventing any fluid from leaking out an el at the stove connection.

Makes a much better, stronger fit than inside.

Single wall. Fits just snug on the 6 inch older thin walled flue. Material for the older first ones was specified 6 inch OD X 12 Ga. steel 5 inches long.
The newer stoves are thicker.

I've measured lots of the materials the flue (pipe outlet) was made of. Drawings for the 8 inch Fireplace Series specify .125 thickness X 8 inch OD X 3 1/2 inches long. The outer dimension specifies 7.990 + - .020 inch.
Of course steel suppliers vary, and if a supplier didn't have what you needed, they may substitute a thicker more expensive material to keep production moving. So one trick was to keep some from an order that may be oversize in case a hole cut in the steel plate was out of round or a little large. The hole could be trued up larger to use a larger diameter pipe saving the time to replace entire back or top plate. I have one with 1/4" thick well casing !

I see no harm in slitting it if hand crimpers don't allow you to over crimp the male end enough. Pry outward to bend the crimped end out to keep it more perpendicular with the pipe wall. Otherwise it will get tapered as you make it smaller.

I don't think it matters. If it was a flue pipe all the way from the top, leading fluid back to the stove, anywhere but the bottom. But in the case of a T, any drip is going to go down the T and not sideways into your pipe anyway. I'm more familiar with Dura-Vent that makes an adapter to go from single wall pipe into the ceiling support box or T. They snap in, and don't come out easily without a lot of wiggling. It doesn't sound like you could get sideways movement to get it back out, with it in that far.

I run one turn open normally with the brown Mama Bear pictured above in my cabin. Little more or less depending on heat required. How much you have to open intakes depends on chimney. Closing pipe damper too much will cause smoke as well. I have an insulated Dura-Vent 6 inch and smoke clears up as it comes up to temp. Once past mid burn when you have more glowing logs and coals than out gassing wood, you should be able to close the damper farther and be smokeless.
You may see a certain amount of water vapor that looks like white smoke too. Especially with colder temps. That usually dissipates in the air not far from the chimney unlike smoke.
When you say seasoned, how long ago was it split, and does it have wagon wheel cracks in the ends?

Key word sizzling. No way is it dry enough. Seasoning time starts when split. It needs to be undercover with air circulation all summer to be ready. You can shorten seasoning time by stacking criss-cross fashion to allow more air through and keep it in the sun - top covered only. Keep it off the ground on pallets or lengthwise runners.
Gray color is just from sunlight, not an indication of moisture. Split wood seasoning undercover won't gray. If you can find some dead wood ready to burn, stand yours on end around the stove to force dry it for a couple days to about a week. Any sizzle is the sign of moisture present and it will quench the combustion zone. Cooler combustion temps = incomplete combustion. That is your smoke. The baffle and brick raises temperature. Higher moisture in wood is easier to get rid of, since the lower the moisture level, the more BTU it takes to remove it. It has to do with wood being hygroscopic, meaning it bonds with water requiring extra BTU to break the bond. So you can remove a high percentage of it fast with heat and air circulation between pieces around the stove.

The only problem with bricks on the baffle is the extra weight on the shelf it rests on. If it gets to near glowing it will bend down. If the baffle fits back against the rear wall it's strong enough, but it can't be supported on the edge and carry extra weight.

Leakage around baffle is fine. Matter of fact it's good to have some since you can end up with stagnet movement in the corners. You want the hot gasses touching the firebox corners increasing their contact with every square inch of firebox they can before exiting.
When you check with a meter, split and check on fresh split face, not the ends.

If it was standing dead, that dries fast. I split and burn after a month criss cross stacking. That's all I burn unless I get storm damaged trees. I always bring in a days worth and keep it around the back of stove. If a storm blows moisture into the stack, I cheat with a few in the open oven.

That oven runs 300 to 350 with door closed while heating the house without turning the oven on. So it's dry by the time it's needed. Heating with a big cook stove has so many advantages.

Yes, you are using the BTU available in the wood to remove the moisture, reducing the usable heat.
Moisture inside the wood does many detrimental things;

Moisture that is evaporated consumes heat so temperature rise is slower. Moist wood is a better conductor of heat than dry wood, so a larger amount of energy conducted on the surface spreads to the interior, slowing charcoal process on surface. Water vapor passing through the charcoal layer reacts with charcoal producing carbon monoxide and hydrogen. This reaction uses more heat energy. Water vapor that does leave the wood, dilutes combustible gasses making them difficult to burn.