How much sweetspot can the average person train up to?

I’m assuming something like Eclipse +1 (3x25 @ 88-94%) is doable for the average person with enough training.

Also assuming your FTP is accurate.

Would an amateur be able to do Pendleton?

Click on the All Rides link at the bottom of Pendleton and you’ll see that it gets completed roughly once a month. Just this week John Barclay completed it with an FTP of 350. Nice going!