Unexpected output from astable multivibrator?
What you are trying to do is the ROSNER MODIFICATION to the astable multivibrater   this was well before the internet and I cant find any reference to it  and yes it can sharpen the collecter waveforms                   A sensible thing for you to do is to increase the caps by a factor of 10 and see some waveform improvement because the astable isn't used at high frequencies