How to add bouncing to a switch in LTspice?
Just use another of the VCSW elements and a different voltage source to control it. Place those in parallel to your existing VCSW. Then set the timing so that it delays until it gets close to an edge you want to test. Something like this:



I've used .PARAM to set F to 500 Hz. The left side MYSW emulates the 500 Hz period of the reed relay. The right side emulates bounce (I divided by an additional 200 to make the pulses short.) Take note of the .22/F delay. The left side uses a delay of .25/F. By making the bounce switch delay a little less, this gets the pulses to start taking place a little beforehand. I also cap the number of cycles to 6 here. But you can adjust as you want.

EDIT: Here are the pictures of the simulator I set up in LTspice, below. You may need to adjust the filter capacitor to reduce the swing to stay within the 4V hysteresis limits. Also, your LED will affect this.

Truly, this would be a LOT easier with a micro. Or using a 7555 as a schmitt trigger, I suspect. This is really overly-complex.