Quick question-

Is the BG class freely available if you don't have sorc levels?

No Black Guard is still limited with out Sorc levels. But it is 10 times easier to get. Often times being able to be gotten with a bio which explains how and why you would qualify for the class. WITH the understanding that you may not take Sorc with said class.

Have another: Is there a use for blood points other than buying the disciplines the npcs give out?

Not really at this time no. But given how things work you should never have enough points to buy all the disciplines anyways that a single person could learn.