7 I have to watch Downton Abbey... or....
Basically, I've just learned to be flexible. I try not see the-music-as-it-is-written to be a rigid "this is the only way it can be" sort of thing, but rather view every printed arrangement or composition as the starting point for our own expression of it. That goes against all of our Western Classical Music School Training, but its the only way to stay sane.
as far as choirology goes
I would suggest that you speak about this VERY honestly, WITHOUT JUDGMENT. I mean literally ask the choir, "I am becoming concerned about our ability to accomplish the musical tasks of the liturgy with the sporadic rehearsal attendance here. What do you all think is a reasonable expectation regarding attendance?" Note the absence of telling them what they need to do. Do not tell them what to do, rather ask what they will give. Sure, you might offer suggestions as things get going, "I feel that you will be more confident at Mass if you attend the rehearsal prior," but again note that it's suggesting WHY they might make a commitment rather than denigrating that they will not make it.
In the meantime, start a new choir- invitation only or audition, with expectations clearly defined at the outset. Teach them interesting stuff.
To participate in the discussions on Catholic church music, sign in or register as a forum member, The forum is a project of the Church Music Association of America.