YES. You force pollen asap and you wait until the seeds mature before you chop, obviously. And just like photos, there will be a number of pheno expressions in autos. Many of them may be shit. So, selfing does make sense in trying to lock down specific traits. I believe this statement holds even more truth with autos given the fact that you are essentially trying to outbreed the shit traits of the ruderalis.
If the OP didnt know the answer to his own questions, I doubt he is going to be able to pull this off. Even if it were possible, it would be an extremely overly complicated and backwards experiment.
The answers to the question "Can an auto be used as a mother plant?" is no. The question itself demonstrates a lack of understanding of what a "mother" plant is anyway.
And the second question "Is there any way to stop an autoflower from flowering?" would also be no. Again, the question seems to answer itself.
The solution: Buy some regular or feminized seeds of the strain in question. Then you can have a mother plants and grow out cuttings indefinitely.
If you want an autoflowering plant, youll have to cross the strains that made up the original strain, then cross that with a ruderalis and eventually, maybe end up with an acceptable, stable representation of the strain that inherits the ruderalis "auto-flower" trait. That is just my basic understanding of breeding. I am sure it is even much more complicated
If all goes well, you have the autoflower that you started out with and the inability to keep a "mother"