The 1987 deed defect is the kind of thing that looks simple and takes 90 days to cure, depending on whether the grantor is traceable, whether heirs are involved, and what jurisdiction the property sits in. Your attorney needs to be pushing the title company right now on the specific cure path, not just the status. A corrective deed, a quiet title action, and a court-ordered reformation are three very different timelines, and the seller's attorney dragging for three weeks without escalating tells you they may not have a clean answer yet.
The assumption doing the most work in your current position is that the lender holds the commitment. Confirm in writing today exactly what triggers a commitment expiration and whether a title defect qualifies as a force majeure-type extension under your loan documents. Some commitments have a built-in cure carve-out; many do not. Your attorney already knows this, so that call should already be happening.
The risk you have not mentioned: your GC. If demo starts and the close slips past your extension window, you have a partially demolished kitchen in a property you do not own yet. That is not just a delay, it is a liability and potentially a negotiating crisis with the seller if they use physical site changes as grounds to dispute the contract. I would put the GC on a conditional hold right now, in writing, with a specific trigger date for confirmation to proceed.
On the preliminary title report: the 1987 defect should have surfaced in a standard chain search. Whether it was missed or disclosed only to the seller's side is worth documenting, because your title insurance policy likely covers you on a missed defect, and you want a clear record of when you requested that report and what was represented to you.
Who issued the title commitment, and is it the same company now flagging the gap?