I'll start a new post to give an update since the last post
deteriorated in a unfounded accusations (I am bearded_malc and not anyone else).
I eventually got interleaving turned off. I'd been told it was off but sync stayed at 7616 with contradicted that. Finally I was believed and it was actually turned off. Now I sync at 8128 and IP profile has gone to 7150. Download/Upload/Ping is 6.75/0.38 Mbs, 17ms. On a good day of course. On old DSL-504 best was 5.26/0.38 Mbs, sync = 6624, IP profile 5500.
BTW TP-Link helpfully gave me the telnet commands doc. Not as nice a DMT gui but the numbers are all there. This was helpful in confirming I was still interleaved. I now mostly use telnet to check my error rates.