Okay, I think the problem is in step 3, "select all, center justify." If you do this, the HTML editing plug-in, which was developed by another company, places one centering tag around all the paragraphs, rather than applying a centering tag to each individual paragraph. Then that surrounding tag gets lost when you save. I can see if there's a way to configure that to work differently.
Meanwhile, instead of selecting all and centering, you could click inside the first paragraph (no need to select it all) and click the centering button, then click inside the next paragraph and repeat. That will take a few clicks, but then the centering will be applied at the paragraph level and should stick.
It looks like selecting all to apply a color is fine, because that is always applied at the paragraph level.