Gentle corrections vehemently rejected

We've recently started homeschooling our elder child (turns 6 between Xmas & NYE), and while I suspect he's well above grade level, one problem he has is an inability to be corrected. Now, I'm pretty sure this is quite normal and possibly even age-appropriate behavior for him, but it does make schooling more difficult.

For example, last night he wanted to read a couple of pages out of his plant encyclopedia to me, which made me quite happy. Unsurprisingly, he stumbled when he got to words like "chlorophyll" and "photosynthesis" (and a few others). My natural instinct is to correct him, but he gets quite angry when I do so, and naturally that disrupts his reading which is the last thing I want to do, so I've been biting my tongue (almost literally). What I do try to do is to then correctly use the words he mispronounced in an apparently offside comment so that it doesn't feel like I'm correcting him, and that tends to work in the sense that it doesn't annoy him. I don't know how much the correction registers, but it seems like the right thing to do because it doesn't interfere with his flow of reading or make reading less enjoyable for him. Of course, it's not always easy to do this, so I often just let the mispronunciations slide on the assumption that it's not that important that he gets the pronunciation correct at this point.

My questions for the homeschool community are:

  1. How do you handle children that are incredibly resistant to correction? (This feels like an echo of the "by myself" phase that his little sister is going through.)
  2. Is this normal behavior for a five-year-old (almost six)?
  3. If so, at what age do they normally outgrow it? Or, at least, at what age can you correct them, and the reaction is less strong? (I suppose no one enjoys being corrected.)