How to write inductor ODE equation properly?
Managed to get that up and running: http://jsfiddle.net/zo2xuhds/embedded/result/

Trick was in a wrong gate logic. A gate must:


transfer power in one direction, from capacitor to inductor, but not vice versa (not sure if there are real-world analogs, maybe triac?..)
open when a capacitor absolute voltage exceeds some threshold Vopen (no matter negative or positive),
close when current will become less than holding current Ihold (again, no matter of its sign)


@SunnyskyguyEE75 mentioned mistake in inductor ODE: Indeed, the Ia⋅Ra is correct term. I've messed resistances up with conductances, which are typically used in neuronal studies. 

Certainly, what was noticed during my home-made research, is that:


Cm(membrane capacitance) and La(axon inductance) are responsive for frequency ranges and may be chosen low and even fixed.
timestep dt(=1) and cap leakage Gm(=1/Rm) are rarely useful and could almost be omitted from model. 
Ra and Vopen are capable of producing chaotic behaviours, and different kinds of tonic bursts: 


Such a simple thing is capable of creating non-linear pwm signals

Very pleased with it, I've finally done that, without using exponentials, and even squaring. Probably that puts some restrictions on the model's computational power, but I haven't figured out them yet.