Basic Toggle Switch Circuit

[AnalogKid]

1. Yes.
2. That's what I get for using someone else's library. Corrected files attached.
3. No. System 5V comes in from the USB connection, and is decoupled by D1 and filtered and stored by C1. +5V powers the 4093 and the turn-on pulse former C2/R1. When the USB 5V goes away at turnoff, U1A inputs go low and drive the turnoff pulse former C3/R3. This works because even though the 5V input is gone, C1 holds enough energy to run the circuit for 1 second, long enough to make a 1/2 second output pulse.

ak

 

[AnalogKid]

Second pass. This one has a single monostable for consistent output pulses rather than two edge stretchers, and a larger holdup capacitor to assure the turnoff pulse. Note that none of the component values or tolerances are critical.

ak