Neofin Blaue isn’t bad at all. I get the impression that with Efke 50, I wouldn’t quite reach 50 ISO with it either, but I can’t test that precisely – others are better placed to do so.
Perhaps you should give Adox ADX A+B a try as well. I’ve come to quite like that developer for certain films. Fine grain, good sharpness, lovely detail, and straightforward processing. It doesn’t quite reach the rated speeds most of the time; with the films I use, it stays about a third of a stop below. But the speeds are a bit on the high side anyway with most black-and-white film/developer combinations. I think the +/- 100 ISO that an FP4 achieves in ADX A+B is perfectly fine.
Wolf:
Page on the Tessina. Yes, it takes 35 mm film.
Philipp