I'm a first year Beek, so my opinion is probably worth what you're paying for it. :-D
That being said, I think adding the second box is a no brainer at this time for you. Deciding whether to continue to feed is a little trickier. Aren't you well into spring? Do you have a flow going on? If so, I'd stop feeding. If not, I'd continue, but keep an eye on it moving forward. If they continue to keep storing so much 1:1 they may not allow sufficient room for your queen to lay.