Thank you all.

I actually went for a 2017 Specialized Roubaix Expert with 33mm tires. It's a first owner bike and in very good condition, well kept, I looked at everything very very carefully, and inspected the carbon for cracks, fissures, nicks etc. It's mechanical Ultegra, and it has a front damper, disc brakes.
I paid $1500. Since I'm going to use it on tarmac around Central Park in the winter and on gravel/dirt/tarmac roads in the Berkshires in the summer, it's perfect.

Best pieces of advice I got here:
-BB is worthless
-used Di2 is a liability
-aggressive fit might not be a good choice
Worst piece of advice:
None really