Well, did the right thing and sawed out the old galvanized fitting in the bathroom and replaced everything below with 1-1/2" plastic, tied it all together with rubber couplings on each end. Came out nice, so I buttoned up the wall, satisfied the job is now right. Kitchen is next, using 2" plastic which'll give me a proper wall drain and eliminate the "S" trap through the floor i was originally planning.
Thanks to all for the guidance.
When gluing the plastic together, I was surprised to find that after inserting the pieces together (pipe to elbow in this case), the parts wanted to spring back apart. I actually had to squeeze them together for about 10 seconds to get them to stay. I've done plastic before and don't remember this happening before. Have others experienced this?