I think it's appropriate to point out that a wooden head is no substitute for a good hard hat. Considering the way you ar going about this, having both would be to your advantage.
As far as the condition of the "joint" in the area where the moisture is, "white stuff" is usually a good indicator that fungus has made itself at home in a timber. How much damage is done remains to be seen. I have more than once witnessed timbers that where as hollow as air ducts due to combined insect and fungus damage. I have also seen timbers that showed fungal bloom but were quite repairable. A lot depends on species and how long the correct conditions have existed.
Your second question actually relates directly to the first. If indeed the frame has been compromised by fungus, it's very possible the plate could remove itself without warning during the disassembly process. Good temporary bracing is critical. Yes a gin pole can work well for for dropping the plates, but with no experience in frame razing and gin pole usage, I would think the cost of crane rental would be inexpensive compared to several weeks off work waiting for that broken leg or arm to heal.
Work slow, safe and smart. You and your friends will benefit.
Good luck Woodenhead.
Keep us posted (yuk, yuk).