Impromptu prepared block reward and net coin supply charts here: http://imgur.com/a/OocoU
Correct, perpetual block reward: 30,000 Siacoins after block 270,000.
Added in edit:
Correct. The other way to acquire Siacoins, besides mining or buying, is to rent out storage space: you set your own price minus a 3.9% tax that goes to Siafund holders (10,000 Siafunds issued; devs/founders possess about 9,000 of those, and ~1,000 were distributed in a crowd-sale to fund initial development).