As long as you get the correct bmp sequence, a still for every bar number it should mux encode them with the audio.wav to avi.
It's a mystery but I'm sure you will get it sorted.

* I just remembered something, change the font size and add a few more rows, as I remember rendering a video once with lyrics and it was fine playing in Biab but was totally screwed up and crammed in the video, but when I reduced the font size it was fine.
The bitmaps in your pic are a bit hard to see but it looks like the chord name take up the whole bar, can you upload a single bmp still, just open it in Paint and save as JPG.