What a great job you are doing! I grew up on Fairfield and I remember that the masterbath had the same leak. My family ended up putting a heavy duty rubber sheet over the lead basin then retiled. Unfortuntly, the white tile didn’t match the original (we were just getting the house up to code to sell). That bathroom itself had pink tile too. It was trimmed with black tile so that could be an option for you….in regards to keeping with the time period. Another idea, you could go with a very light soft gray tile. After reading your blog, I’m confident that whatever color the two of you decide it will look amazing.
(One day I hope to be able to move back to that wonderful neighborhood….I’m keeping my eye out)