You can admit that you've been overwhelmed in learning the ins and outs of a paper and trying to learn the writing styles as well. If they point out your mistakes, own them and tell them and tell them you will attempt to do better. You may not want to dwell on the mistakes, but you will have to listen to what they have to say and then you can state your opinions.
As for the perf. editor, you really do give him entirely too much head space. He's nothing more than a human being attempting to get a paper out that is error free. Stop allowing him to put you in a vulnerable position.
You are mind reading about why they are having this meeting. They are having this meeting because you are not performing at full speed and they need to figure out what or how to get you to that level of work. Your resume and interview came across that you could do this stuff and you wowed them at that time and now you aren't performing to their level of expectations, so they need to find you a good place on the paper because they know you relocated to come there to work on the paper.
Yes, be honest and stop trying to placate them w/answers that they want to hear. You already know that you can't do it all, so why tell them otherwise. The others that have done all of those tasks probably had been working for papers for years...you are fresh off the boat of being a stay at home mom and homeschool teacher. Those careers are totally different from being in the world of work and papers.
So what if the editor is planning to show you a paper that he worked on. He's trying to help you by showing you the paper and what he did. Instead of always thinking that people are trying to get at you, start looking at them as trying to provide you guidance and assistance. They have tried to work with you since you got there and are still trying to be patient and help you find a proper niche. They see potential, but they don't know how to tap into it. Listen to what they have to say, write down things and don't walk away thinking the entire meeting was negative.
Do not offer to resign. You've got this paper covered, you need some help and even if it means transferring you to another part of the paper...go for it.
Now, go to the meeting and stay positive.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
