In my experience you can't hope to change a person at your first few confrontations. Just work at making a couple of significant points, and end it non-confrontationally - leave an opening for another conversation. But that is just my experience.
It seems the best witness to your mom may just be how you live your life. That doesn't mean you have to be a goody-goody or anything, but show her that you can make choices and good things can happen even when not a JW. (Did I really just say "goody-goody"?)
Honestly that may not even work for a few years. And to be even more honest there is a perfectly good chance she may never come around. But that's the breaks man ....
I agree with others that the ball should always be put back in HER court. Put the burden of proof on HER and/or the organization. Then whenever she makes her guilt-inducing or humiliating comments to you, remind her that you are perfectly willing to come back to the bOrg, but you are "still waiting for her proof of [insert topic here]". That will shut her up. Don't let her bring elders with her unless you are up for that kind of tag-team situation. Tell her it is between you, her, and "Jehovah", and that she should be able to make a stand for her faith.
I am not sure what you have thought about this, but you may want to even consider not telling her about your "apostate" contacts yet. Once she hears that the shields will go up and you will never get a point across - and even if you do she will simply dismiss it as apostate reasoning by that point. Let her chew on it for awhile (maybe months) before dropping any hints of apostate stuff. If she asks you directly - just lie and say "no way, I don't want to have my reasoning tainted" or some crap like that.
As far as complimenting you .... um ... I'll have to give that some more thought .... I'll try and write something tomorrow!