Ric,
1) The LEDs are a fairly crude measure of signal strength. You can fine-tune the alignment for maximum signal strength, as displayed by the The "signal-strength" field on the "/interface wireless monitor 0" display. I suspect a lot of folks would be pretty happy with 4 out of 5 LEDs lit.
2. Control-C will end the pings, and will also end other commands such as the monitor command above. Also, you can tell the router to only issue x number of pings with the command (From Winbox):
/ping a.b.c.d count=5 (or whatever number)
Also if you just want one "snapshot" of the state of the radio:
/interface wireless monitor 0 once
3) 22.9 as measured at the radio is plenty. I believe that AWG 24 wire (such as in CAT5) has a resistance of about 1 ohm per 12 meters, so there should be a fairly predictable voltage drop, depending on the length of cat5 cable, and the current draw of the radio.
4) A client license comes with purchase of a Mikrotik Routerboard. Other devices may vary--such as a PC that requires a license purchase to run RouterOS.
John KX7JM
John C. Miller
(530)873-9005