(From Artscroll Book on S.A)
A. If its Sukkos you must live in the sukkah
B. If its S.A sitting in the sukkah is belittling the holiday.
4. Mordechai/Ravyah- Not saying the bracha alleviates the issue of belittling S.A b/c by not saying one you indicate that you are just in the sukkah b/c of a doubt which is not considered belittling.
5. Basically:
A. Sitting in the sukka for both meals is based on this idea that just not saying the bracha makes it not a zilzul.
A. You say Shecheyanu at night for S.A so how can you say that in the sukkah.
B. Its reasonable to say a person would eat in the sukkah if not obligated but not to sleep.
8. The Gra and others (see Shar Hatzion there) say to sleep in the sukkah