I suggest you write it as 3 endings. Build it as a linear song and then add the repeats.

The common section is "A" as you describe. The first ending is simple - let's call it "E", the second ending is E plus B, and the third ending is probably a modified E to include any special finish.

Then build the 1st, 2nd and 3rd endings in the dialogue, recognizing that the second ending is longer than the first.

I build almost all my songs this way, and can generally print them on two pages by carefully managing the bars per line on the fake sheet.

One tip - don't make the first ending too short. I usually make mine 4 bars, and print it on its own line, it will make lining up the print so much easier. I rarely use DS as it often is just as easy to make a third ending. I reserve DS for breaking out of the "A" section early if the third pass does not need a full "A" section.

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