3.) Once it starts slowing down I am stopping the bitcoind.service for 12 hours, giving it a rest. This is just in case there is some kind of weird throttling going on.
This step doesn't help.
5.) If slow, then I am going to order this -> Beelink SER5 MAX RYZEN 7 5800H Mini pc office + Ram32GB + Storage 1TB
That's more than sufficient to do a quick download.
This is one of those particular things that becomes more and more resource consuming as it goes along, still working but going slower and slower.
Correct.