1) when a leader "calls" you to a position that would require you to do or say things that, frankly, you don't believe?
I'm not sure that can be done. I don't want to minimize the struggle of others getting to where I am with regard to this exact issue, but nothing and nobody can "require" me to do or say things that I don't believe (mostly because I simply refuse to do so) - and I've been on a High Council and in a Bishopric, for example, and been thanked for providing a different perspective on discussions. The key is being comfortable BOTH with my own beliefs AND the responsibilities of the calling in which I serve - and being willing to be open with those who extend callings and assignments to me.
For example, I was asked once to chair the Melchizedek Priesthood Preach the Gospel Committee in my ward. I was clear that my suggestions and leadership would be based on why those committees often are useless wastes of time and totally ineffective - and that I would be proposing some non-traditional approaches that might be seen as radical by some members. The High Priests Group Leader said, "OK." I accepted the assignment, since if he really wanted me he had to accept ME.
The key is that he knew I'm a "faithful member" - that I care deeply about the Church and its members regardless of differences in specific beliefs (and that nothing I proposed would be selfish in nature, and I wouldn't pitch a hissy fit if what I suggested wasn't approved). I might argue privately, but I would never make it a public fight - and I would stop arguing privately once he made his final decision. The one thing I could promise, however, was that I wouldn't teach anything I didn't believe.
2) when a leader "reprimands" you by quoting a scripture that implies that your actions are against scripture?
I either quote another scripture or prophet back at them with a HUGE smile on my face (if we are friends and he understands my twisted sense of humor), or I thank her for her concern, ponder it seriously and deeply, see what I can take from it to help myself understand her or the principle better, then make a change or continue as I have been - depending on the outcome of all the stuff I just outlined. The key for me has been to assume there is SOMETHING I can learn from the reprimand, even if it only is greater charity and understanding of other good people who see things differently than I do.
A former Bishop told me once that he deeply appreciated two things about working with me:
1) I told him exactly what I thought, both when I agreed and when I disagreed with him;
2) I said, "OK," and supported him when what he decided to do wasn't what I had suggested.
Very few things are worth fighting about, and a reprimand doesn't even come close to that level of importance.
3) in general, when another member (leader or not) talks of you needing to repent of an action that you really don't feel is wrong?
"Thank you. I appreciate your concern and will think about what you have said."
Then I try to act as I've outlined in response to #2 above. I try hard not to be defensive and to try to model for them how I hope they would respond if I ever felt prompted to reprimand them or call them to repentance. After all, I believe the most important aspect of life is repentance - meaning simply "change". If I can't try, at the very least, to be open to observations of others that might point out changes I need to make, then I probably won't change much - and that would be a shame.