Try again on the 29th
Fincke got a feel for an EVA anyway. With that he might be more comfortable making the long trek from the Zarya module to the Unity module for the repairs.
The good news is there are spare Orlan suites available if they can't find the problem with the pressure drop of his oxygen tank.
I assume they are using the upgraded Orlan suite in coordination with ESA.
Yes, Mir set a lot of examples and successful Mir operations should ease concerns of an empty station, but ISS rules are being broken or compromised and mainly because of the Shuttle's status as you know.
SteveS