1) Where should we park when we arrive for our tour? 2) Do we end the walking tour at Christian Moerlein at the river? If so, how do we get back to American Legacy Tours to get our cars?

I would park at Washington park garage. You end the tour at Christian Moerlein in OTR not at the river. It is only three blocks from Washington park

After the tour make sure to walk down to Rhinegeist Brewery. It's only a few blocks away from Christian Moerlein.

Find street or garage parking, nowhere specific. You end at the Moerlein Brewery in OTR, not the lager house, so it's a short walk.