Hey I commute to downtown every day from mount Lebanon. The worst part is west liberty avenue. I would also be interested in finding an alternate route. I take pioneer sometimes and that can be less busy you could try that.
I think the last high level T stop for you is Fallowfield or potomac. then you could get off at station square or first avenue station and pedal into work. keep us updated if you find a safer route because I would be interested in taking it too.