Update (October 22): After 12 days in "Waiting for Review" with no movement, we removed version 1.1.14 from review and submitted version 1.1.16 instead, together with the same four in-app purchases, and requested an expedited review again (confirmed). The new build also includes the user-generated content moderation features directly in the binary. I'll post here once there is any progress. Thanks to everyone who looked at this thread.

Update (October 17): On October 15 phone support became available again and I spoke with Apple Developer Support (case 102997214371). They said to expect movement within 48 hours. That time has now passed, and the submission is still in "Waiting for Review". I've added a follow-up to the case. If anyone has gone through something similar and found what helped, I'd really appreciate hearing about it.