iPad - Downloading Messages from iCloud not working

Turned on iPad Messages in iCloud after doing the same on an iPhone, and while viewing online iCloud (Safari MacBook Pro) after Uploading from iPhone, it says there should be about 48MB ("Settings" shows Storage Usage), but:

While in Messages on iPad it does show "Downloading Messages from iCloud..." at the very bottom of the Messages list on the left with a gray line that looks to be pretty far along if that is a progress bar. However that goes away after several minutes, and while maybe 20 Messages or so were downloaded initially (out of probably hundreds), but none since. All the "restarting" of the downloading in the world doesn't get more Messages to show up on the iPad.

The only way I've found I can "restart" the downloading is in Apple ID/iCloud (on the iPad in Settings) - to turn off Messages as an App Using iCloud, tap "Disable and Download Messages" in the alert since it warns that not all messages have been downloaded, then turn Messages On again for iCloud.

Does anyone know if indeed though the "Downloading Messages from iCloud..." and possible progress gray line, the downloading is still going on once that info at the bottom of Messages disappears? Perhaps my "restart" method to get the "Downloading..." message back at the bottom of the Messages list is actually making it start over every time? Just leaving it after the Downloading message disappears for a long long time does not yield more Messages or higher iPad Storage usage for Messages...

Again, no new Messages ever show up, and the General/iPad Storage for Messenger seems to come back different every time - sometimes higher, sometimes lower - though tapping the MB amount (6ishMBs to 9ishMBs) does show "Documents & Data as the same as on the previous screen, but below "DOCUMENTS" a tally shows Photos at 36MB, Videos at 6.1MB, and "Other" at 152KB, and those tallies do not change. (Possibly just numbers returned from iCloud about what should be downloaded - tapping any of them does not show any Photos or Videos, etc.)

Full disclosure: We live in a cabin in Yosemite National Park and the DSL internet speed barely hovers above 5 or 6MBS.

Other trouble-shooting: Sending both an iMessage and plain text (logged out of iMessage on my phone for the plain text) to the account the iPad is associated with in iCloud do not come through to Messages on the iPad. (I've got the iPad logged in now to my 93 year old dad's Apple account - his name is "Apple" too - and all this effort is to try to clean years of junk Messages off his new iPhone that got transferred over from an AT&T phone - which for some reason do not get removed the normal way, which is to change the Keep Messages to "30 Days" in his settings and tap the Yes, Delete them. Years' worth still remain, and are clearly "click bait" and worse since he never even looked at Text Messaging before...)

I'm trying to get it in my court to painstakingly select all the messages and delete them then have them gone from his iPhone via iCloud syncing. Trying to walk him through (via phone) removing all those Messages on his iPhone is kind of a non-starter. Edit/Select All sure would be good, but alas - maybe in iOS 15?

Any hints or pointers appreciated!

Rich Apple

(iPad 8th Generation, Wifi only, iOS 14.7.1, but for some reason that was not available from pull down list, so chose 6th Generation.)