Remediation began with jacking the ridge board back in place.
Initially, the author cut temporary support blocks from 2x4s and posted them down to a center bearing wall (in line with the center girder supporting the first floor).
The final solution was to build a short wall, starting with top and bottom plates.
Before infilling with short studs, the author jacked the top plate up as much as possible to push up any rafters that had dropped down.
The framed wall that supports the rafters is put together with screws—installing those proved much easier than trying to swing a hammer or use nail guns in the tight attic space.
For good measure, the author shimmed any remaining gaps between the rafters and the ridge board.
Rafters abutting a header at the block chimney had dropped. The author jacked those individually and attached the rafters to the header with joist hangers.