AC1000

> I purchased the AC1000 [...]

   Is that a model R6080?  Look at the product label.

> [...] and was told it had an on/off switch for wifi,

   Were you told where it is?  Visit http://netgear.com/support , put in
your (actual) model number, and look for Documentation.  Get the User
Manual.  Read.  When I do that for an R6080, I don't see such a button.
The only prominent button I see is the "Power On/Off button".

> [...] When the wifi button is pushed off on the AC1000 the other
> harwired devices aren't connected to the internet. [...]

   Actuating the "Power On/Off button" could account for that.  What
happens to all the LED indicators when you push that "the wifi button"?

> [...] i have a spectrum wireless modom which only allow me to connect
> one device [...]

   Does it have a maker and model number?  If it's really a _wireless_
modem, then it's probably a wireless modem+router, and you'd also want
to ensure that its wireless radio is also off.  (If, that is, you really
believe that a wireless router can affect anyone's health).

   If this (unspecified) "a spectrum wireless modom" has been configured
as a modem-only ("bridge mode"), then its radio may already be disabled. 
That would make some sense, if you're using it with another router
(like, say, an R6080).

> [...] is there another way i can use 3 devices hardwired to the
> internet without wifi turned on while the others are in use? [...]

   For a start, don't power down the router?  You should be able to
control the radio(s) from a computer/device with a web browser which is
connected to the router.  Look in the User Manual for "Enable or Disable
the WiFi Radios".

   Some other Netgear router models do have a "WiFi On/Off button".  For
example, the R7000.  (Repeat the procedure above to see the R7000 User
Manual.)

> [...] Does this call for use of a switch? [...]

   Not an Ethernet network switch.  To use multiple devices you need
some kind of router.