The overall orbit change capability of the shuttle, even if you filled the payload bay with extra fuel, is less than 5-8 deg of inclination change (and return) or a reach up to -maybe- a few thousand km of altitude. And that's with 50,000 lbs of extra fuel. That means that from the ISS orbit, there are effectively NO satellites that could be reached for repair, as all the LEO stuff is either in lower inclinations (0-28.5deg) or higher (70-110deg) compared to the 51.6deg ISS orbit. All the medium altitude stuff is too high (10-15,000km), in a high inclination (60-80deg) and the crew would be killed by the radiation belts during the repair.
All the GEO stuff is low inclination AND too high to be reached.
Basically, the only thing you could reach from the ISS is, well, the ISS, even if you dedicated the entire payload capacity of the shuttle or an EELV-heavy or falcon-9 heavy for fuel.
Sorry.