I worked my way through all the options, and found what I had missed the first time.
I turned smooth scrolling off, and that gave me the jerky but more exact scrolling that I was used to. I prefer it like that.
I no longer have 9 white rectangles on new pages. I told Firefox to remember my history, and once I did that, the rectangles became filled with thumbnails of the websites the last time I visited them. Now it looks colorful and pretty, but I don't know if it's very useful. It doesn't appear to be any faster than going to the bookmarks.