by pass the valve on the rear, and that will be fine.
your need new brake lines up front, unless you ad to them to get them back as they should.

yes the fiesta has the cross braking system.

i wouldnt use the little vlauves on the mk5 cyclinder though, get some pre set valves off a non abs frst as seen in the pic below.

as for the connecting rod on the servo, i cant remember off hand if it need to be made longer or shortend