You should only need one GFCI device per circuit. More than that causes problems.
The outlet could be wired many ways. Open Hot means there's no voltage on the hot leg, so typically that's because something is "off". I have an outlet on the same breaker as my pool timer, but it is in series after the timer. Meaning my timer has to be in the "on" position in order for the outlet to work. Something I should probably fix but have learned to live with. I suppose it could be normal for the outlet to work only when the light switch is on; it just depends on how the original owners wanted it wired. It's easy to test if that's true or not, at least.
If both the light and outlet are on the same circuit, and with the switch on, you get no light and an "open hot" on the outlet, I'd suspect the circuit breaker next. Is there anything else on that circuit that is or is not working?