Hey Wiz, I'll try to help ya with some of that confusion. On the mano, (I assume its the Dwyer model 25) most of us use the positive side of the scale (I believe its the low side) to read negative pressure. You want negative pressure so carbon monoxide can't leak out. I think a manual damper between the baro and stove is a good suggestion.
Now, air tight room verses not an air tight room. An air tight room (the room your stove is in) should inhibit a strong draft since make up air isn't able to replace the air that the baro is taking out. I think this issue got some high profile on another thread somewhere lol. How can I prove this? Well, on warm days I open vents in my furnace room to the outside to aid a lazy draft.
When its windy I'll close my manual damper about 80% if my baro can't maintain less than a .05" WC as read on the positive side of the scale, knowing its actually negative pressure. The only reason for hooking them up "backwards" is so we have more scale to use, since the negative side only reads down to -.05.
I hope I've saved you some hairs