The pictures would indicate that you have significant settlement taking place. This type of thing doesn't happen overnight, but usually over an extended period of time. I've seen similar cases, and most were the result of changes in the foundation support material, usually caused by excess water getting to below the footings. Chances are your house's footings don't contain any longitudinal reinforcing steel, which would have prevented what you're seeing. Except in seismic zones, the IRC (International Residential Code) doesn't require footing rebar, which I always thought was strange.
I know you don't want to hear this, but I don't think there are any cheap and quick fixes for the problem. While I don't think the place is in danger of collapse, you should look into getting quotes from foundation repair specialists. Helical piers can be installed externally, and will raise the settled corner back to its original grade. Mud-jacking is also an option. A good masonry contractor can repoint the unbonded brick and block mortar joints, along with filling the open slab corner crack.
If money is tight, talk to your mortgage lender to see if they'd consider a home equity loan to cover the cost of repairs. The lender might look favorably at helping preserve his/her investment.