The theory of why witches are more powerful make absolutely no sense at all.

So, one of the priests brought Eragon's flame and it was used as a catalyst. The problem here is we have zero foreshadowing, and nothing to hint it was his flame. It's a huge jump to just think we will get it, directly. I enjoyed the story so far and I will still continue to read it as you are a good writer but here you made a mistake. it can easily be arranged if you modify the last chapter. Write with a little more details. let Ciri ask her sister since when she knew how to do magic or something like that. She only has to respond, it's not mine and we will easily get it. And even then you should have shown another person perform the magie and show how their flame had different color. We will then knew that Eragon's flame is a special golden one.

it's not the fact they will obtain dragon that is off-putting but how they managed to do it. In my opinion, you should rewrite this chapter. If anyone can hatch a dragon just because they have one egg lying around and a few droplets of Targaryen blood in them, it diminish greatly what Eragon accomplished. You can either make it so they do it in a different way, or use blood of Eragon.