The problems you describe are difficult to diagnose by words alone.
Let me just list some types of "fixes" I have seen, and recommend that you bring in some structural engineer type contractors to give you some estimates or at least pick their brains for ideas. Be honest with them if you don't intend to hire them to do the actual work, by offering to pay for the consultations. ($50-75/hr should cover it for most people, except for actual structural engineers)
I have pumped concrete through floors to fill voids in the soil below. This can do very interesting things, and should be done by an experienced subcontractor who knows what they are doing.
If the settling is really bad, or your foundation is beyond repair, you may need to lift the home and redo it altogether. $$$
Sorry to hear your situation, I don't envy it. Have a good day!