Positive feedback using series resonance

I wont call it feedback. What you demonstrating is a loosless resonator, a perfect tune one to 1kHz. The impedance of this kind of notch is 0! Ohm while resonating. This is only here within the simulation and reality there are many parasitics which would avoid this 0 ohm case. The most importante effect would be a serial resistance of the inductor (around 10Ohm maybe). A parallel resistance can be seen as load to a perfect high pass which is tested at corner frequency 1kHz. Driving with a rectangle gives a amplitude spectrum of 1x1k,1/3 3k, 1/5 5k, .... and what you see is the filtered result

Even you added cap and resistor its still no feedback, because internal resistance of AC source is 0 Ohm and dominates the input of opamp. You need an additional resistor in serie to ac source.

Ok, back to the original circuit, and now?