house flicker

I would like to add a ceiling fan to an existing circuit. There is a single switch on the wall that controls some lights in the hallway. The wire running from the hall light terminates at this switch. How do I connect a new switch ( to sit beside the existing one) to control the fan and use the same source of power?

1.) Wiring of (2) 3-way switches & (1) 4-way switch with 3 each, 4 foot dual fluorescent fixtures. Is the following correct? Breaker box (Power) to first 3-way switch thru 1/2" EMT into top steel switch box, using one NM-B 12-2 w/ground to switch. (White) Neutral wired all the way thru (bypassing switches) for all switches. Out feed (Black, Red & Ground) to 4-way switch from first 3-way switch, thru side of 3-way switch box with 90 degree EMT fitting, using seperate 1/2" EMT, using NM-B 12-3 w/ground. Connect to 4-way switch in thru top of 4-way switch box w/1/2" EMT, outfeed from opposite side of 4-way, thru side of 4-way switch box with 90 degree EMT fitting, also with seperate 1/2" EMT, also using NM-B 12-3. Here is the unusual part. Since the final 3-way switch is over 40 feet away, to save on EMT, the NM-B 12-3 from the 4-way switch was run thru the lights (all of which were connected with EMT), WITHOUT connecting 12-3 feed run to ballasts. Wire was run as unstripped NM-B, to the third 3-way switch. Now, IF I cut the 12-3 at each light, wire nutted the red to red at each cut, and black to black at each cut, for a pass thru (without connecting them to the lights ballast at this point); but connecting the white and ground at each light, as I go, and terminate the white (neutral) the last ballast. The ground would also pass on thru to the final 3 way switch, from the last light ground connection. At that point, the 12-3 NM-B would be proceeding thru the final 8 feet of EMT to the final 3-way light switch, with the red, black and ground going as previously described, as a pass thru to the incoming feed side of the switch. The CUT white going thru the final 8 feet of EMT to the final 3-way switch would NOT have been connected to the termainated White at the last ballast, it would be an empty wire. That particular white wire would be taped with purple and black tape at each end (for identification as a return hot), and used as the return feed "black" for the light ballast, to complete the circuit. From each light ballast, a SINGLE black wire would be wire nut connected to the "white converted to black" and run to connect each light's ballast with an individual black wire back thru the EMT, and terminate on the final ballast going the other way. With this scenario, could I get by with running a single black wire thru the lights connecting EMT tubing, eliminating the over crowding of the EMT at the final 8 foot run of the tubing. Would this seem acceptable???