What difference between maximum line rate and actual line rate is typical?

[#1]

As the title says, what is typical. I'm particularly interested as my actual downstream rate is fairly different from the supposed maximum, whereas upload is similar.

Upstream line rate (kbit/s):
19096
Downstream line rate (kbit/s):
65897
Maximum upstream rate (kbit/s):
19125
Maximum downstream rate (kbit/s):
83036

[#2]

Looks like you've got interleaving on your downstream, this would've been switched on to make your line more stable.
It'll sort itself out when the line becomes more stable, and you should get near full whack judging from the info you've provided.

[#3]

I think you're right. However it has been syncing at ~66Mbits/s for at least a year. Was syncing at 77Mbits/s before that for ages but I think the DLM has just been rubbish since then.