That doesn't control how aggressively the server connects out to other servers though - it limits how rapidly the server processes inbound requests; upping the window from 60s to 1s means that it will only process 10 requests from a given server in a 60s window (rather than 1s window) before deliberately falling behind. Interesting if changing it helped your problem; not sure how to interpret that.
# The federation window size in milliseconds
#federation_rc_window_size: 1000
federation_rc_window_size: 60000
That's how high it needs to be set, apparently.