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what type if boiler? I would not use primary secondary unless you have a boiler that specifically call for it

Conventional cast iron, copper tube or electric could be direct piped

Baseboard is sized at the "average water temp it will see. A conventional boiler is usually sized at 20 degree TD between supply and return. So with a 190 supply and a 170 return you would size the BB at 180 degree. The lower the water temp you run the more fuel you will save but it requires more BB to do the job.

Water flow through the BB should be 1 gpm for each 10,000 btu when using a 20 deg TD

If you are using a mod con boiler you have more flexibility in design. Lower water temps and wider TDs can be used but the design will change completly.

Not really. The baseboard manufacturer gives you the BTUh per foot at various temperatures. You know the temperature you are feeding them with. You know the room heat loss. That's about it.

I hope you are piping them either reverse return or individual source/return to a manifold…

It may be too late, but it sounds like you could have added 2" of polyiso foam under the siding without too much trouble. That would have made your house substantially more comfortable.

An ounce of insulation is worth a pound of hydronics.

I would still do a heatloss regardless of future improvements. If you size the system to a worse case scenario you can always adjust water temperature as the envelope tightens up. It's rare to have too much radiation. Of course in your case too much radiation will have an effect on your wood stove rig with out attention and mixing of return water.

Water jackets or inside HX are probably gone due to market needs and/ or liability issues. Always protect a HX with a safety relief valve. And dry firing them can lead to a big problem if water hits a red hot device. So a bit more than most people think about. Concept is simple enough, but it needs to have attention to detail.

!/2" copper will not allow much flow, if you use small tube, header it like this.

If you pipe like this, heat output can go directly to the load without need int to heat or travel through the tank.

I'm not sure you need the second tank however, unless you add an element for a second heat option?

My concern is if the stove will be able to keep up with what size load? Make the flow adjustable so you can gauge the heat output to keep the stove from condensing, forming creosote.

A protect valve at the stove hx could be another option, it automatically keeps the stove HX in a safe operating temperature range..