Question Two: The electric field is uniform (constant). Why do you think it isn't? See http://www.studyphysics.ca/30/fields.pdf" to check your understanding of electric field lines.
Question Five: Yes. Since you are interested in the outward flux and the enclosed charge is positive, the flux through the surface is indeed, positive.
Question Six: You have the right idea, but I wouldn't use the word enclosed since the Gaussian surface doesn't enclose the negative charge. There is an additional [negative] contribution of flux through the left end cap due to the presence of the negative charge.
Question Seven: Are you sure that the electric potential is lower at A than B?
Question Eight: Again, are you sure that the electric potential is lower at A than B?