WordPress Editor Quirks

The WordPress editor is driving me nuts. I spent a lot of time getting my Music Calendar page looking right, but every day it totally strips my HTML out and I have to add it back in again. When I update it with new posts, it strips out all the spacing I had inserted to separate artists on the same day, and I have been adding back a double line break (br) to make it so they don’t run together. Once I get preview to look right again, I publish it and then I go through the same cycle the next day.

http://dpw67.wordpress.com/music/music-calendar

It’s very frustrating, and I haven’t figured out what the best combination is to make this work. Perhaps someone else might be more familiar than I am with WordPress editor tips, techniques, and quirks. I would appreciate any suggestions that would help.