On my iPhone, iCloud appears to be in an inconsistent state with respect to photos

There are a number of problems I’m having with photos on my iPhone and I’m wondering if it boils down to this: iPhone seems to think I have 2k photos on the phone when in fact there are 20k photos.

I have 20k photos (fifteen years’ worth) on my iPhone, the majority taken by the iPhone. The majority of them are sync’d into iCloud as evidenced by my iPad reporting 20k photos when in Library > All Photos, scrolled to the bottom. There are at least 100 that are not synced (the 100 being on my iPhone from the past week but not yet on the iPad - who know what else isn’t sync’d. I don’t trust it).

I’ll note here the iPad is perennially stuck in “Syncing”, though in iCloud storage it will show “Synced just now” - here’s a screenshot which includes the latest photo taken on the iPad - a screenshot of the entry for photos in the iCloud storage screen:

On my Mac, it shows the same as the iPad, including the the screenshots I just saved on the iPad.

Meanwhile, my iPhone seems to believe there are only 2k photos:

Until now I had assume that it was in the process of syncing 2k un-sync’d photos until I noticed this, under Privacy & Security screen for photos (where I have temporarily turned off all apps’ access to photos):

So the iPhone appears to believe there are only 2k photos when on the there are in fact 20k photos (never mind the 600 videos).

And, yes, there are 20k photos in the iPhone’s photo app. I’m obviously not going to count them but I know the difference between 2000 and many thousands.

At this point I’m thinking I’m going to

• wait until the photos that are clearly not uploaded yet - the most recent 100 which I most definitely need to retain - are uploaded, either because they’re in iCloud or turn Lightroom access to photos back on, load them into LR and let LR store them in the Cloud
• turn off “Sync the iPhone” in iCloud Photos, select “Remove from iPhone” to delete all photos
• turn sync back on again to reload photos
• If that doesn’t work, backup the phone, wipe it clean, restore

Anyone have any other ideas, besides the usual suggestions of upgrading to latest iOS version, signing in/out of iCloud, reading the occasionally useful KB articles, etc.