I have two questions. Can I bring my siddur and tefillin into the mikva changing room (the tefillin are in a felt bag, plus a plastic covering bag, and then both are inside my rucksack)? Second, if I have a copy of the Talmud in my rucksack, but need to go the toilet, can I do so?

If the siddur, tefillin or other sefer are double bagged, they may be taken into the mikva changing room or a bathroom.