1.As I do not know the precise location of your husband's cyst and where it is in relation to the arachnoid space (normal CSF space), it's hard to give an accurate opinion, but generally speaking yes, there are other options. Endoscopic procedures seems to be the new thing right now where they artifically create connections between the cyst and the arachnoid space where it can then drain there naturally, relieving the pressure and volume in the cyst or they can just drain it using endoscopic methods. CT guided aspiration or withdrawal of the fluid is another option as well as surgical excision.
2.Infection and shunt malfunction resulting in over or underdrainage.
3.Yes if there is malfunction as stated above, can present with headaches, visual symptoms, nausea and vomiting depending on what's going on with the shunt.
4.If it continues to grow and starts to push on certain structures of the brain, it may affect the functions of those structures. For instance, depending on exactly where it is in your husband, it may affect frontal and temporal functions such as speech and right sided strength.
5.I would get in a touch with an academic center and ask if there is a neurosurgeon who deals with a lot of shunts if that's what you're considering or endoscopic procedures. Dr. Luciano here at the Clinic does both. Good luck.