How to generate 2-FSK signal from the bit stream(symbols)?
Why don't you use a colpitts oscillator with varactor tuning so that data can modulate the carrier frequency between two limits. You can keep the oscillator stable using a phased lock loop such as the ubiquitous CD4046 - this would also use the varactor diode to keep nudging frequency to the nominal midpoint.

Basically it's an FM modulator. It's basic output is a sinewave so no real issues about using a filter to keep it clean.  I realize "FM modulator" is a tautology so please no need to remind me.

I don't know what you're planning to use as receiver but half the work is done with the PLL circuit - it can be used as a detector.