Also, I'm waiting for a steamrep report to be archived on my brother, but it hasn't been looked at in 3 years. Should I wait a few more years for it to be finished, or can I appeal on outpost earlier?

"This is Eclipse's brother tuning in. I'd like to confirm that he did scam, but he's also learnt to behave better online. If any contact with the original victim can be arranged still, we'd both be happy to make it up to him. After 3 years, we're still waiting to see the outcome of this. Cheers!"

After 3 years, you had plenty of time to do your own research, find your victims and pay them back. That never happened thus, your ban will remain in place.