The Alembic store usually displays instruments that are in stock at various dealers, not for you to order direct from the factory. Look at the listing and it will tell you who you need to contact if you're interested in it. Those questions you have should be directed to that dealer who can tell you what they can do for you.
My guesses are as follows:
No, you can't get credit for the case from Alembic. You may get credit from the dealer who can then keep the case for a bass ordered to replace the one sold to you, but that's a negotiation item. Especially for a 36 scale instrument, the case may be ordered to fit it and not work for other instruments of different build specs. Ordering a road case should be no problem, though.
Strings? Probably a regular CX-3 set. It is medium gauge: .045 - .065 - .080 - .105 - .128 for the five string set.
Looking at the bass you must be talking about, the contact info is:
B and B Music
205 S. Dual Hwy
Camden, DE 19934
(302) 697 2155
After all, there's only one 36 bass on the list...