It's like deja vu

Do they sell you a box to jack into, or a box someone else jacked into?

You change people's minds when they have respect for your expertise on the subject, not when they feel stupid around you.

Live your life so that you are approachable and contemplative.

Exactly.

As does your post.

Why on earth do you think making someone feel stupid is a pro tip?

A flat earth can still be round.

The earth is a SPHERE

There, how does it feel to be proven stupid?

Is it an outside wall?

Sounds like a sweet gig to me

Not sure the size, but if you search for 'furniture cam locks' you should be able to find what you need.

Pretty safe assumption that these shelves were designed to also add to the rigidity of the cabinet

The first thing is to fully assess the extent of all the damage (you don't want to hang new fascia and soffit from rotting rafters).

Poking around with a screwdriver will reveal areas of heavy damage, but finding nothing with the poking around won't fully rule it out. At some point you will have to start demo to know the extent of the job. Contractors know this and it makes estimating not only the cost but the amount of time difficult. So at times like this where they have more work than time, getting someone to even look at it is near impossible.

Like finding a job, finding a contractor is aided greatly by networking. Ask everyone, including strangers who they know. Don't rule any lead out. Maybe someone knows a local retired guy that can walk you through it (you do the work, they drink your beer).

Has any of the rot migrated to the roof sheathing or rafters (trusses)?

Is there flashing, or evidence there was flashing at one time?