1/
it is possible for "x and y" to be singular, if "x and y" is regarded as a single unit.
e.g., rhythm and blues ("R&B") is the name of a popular style of american music. this is one type of music--not two--so one would write Rhythm and blues is especially popular in the South.
most importantly, though-- if this sort of thing ever happens, there will be solid proof in the sentence.
e.g., in OG 13th/2015 problem #85, "owning and living" is the subject of "is", so you know that it's singular and can therefore be represented by "it".
2/
yes.