1) If I remember correctly, Kadee offers a "special" shorter gear box coupler in O Scale for such applications. I think it may be the 806, but you should probably double check the Kadee website.
2) Yes, I have found the the Kadee 800 series couplers will couple with many brands of "claws". However the newer 700 series, will not in most cases. I have been using the newer #740 Kadee since they came out.