> I'm open to any suggestions or ideas.  Thanks!


Playing the heretic here, this would be trivial on an AVR, possibly even the
1200.

I've done bit-banged serial on the 84, using an int on the start bit to get
me into listening. It worked well at 9600.  The idea was to use single
samples at the center of the bit times, based on the edge of the start bit.
The timer was used to trigger the subsequent samples.

Lots of effort though, for what would all (including your PWM) be handled in
the background, almost codeless, on the AVR.