Well, I think we are giving up. The Ritchie stem is about equivalent to 8cm, with some rise. It is still way too far. More than 3cm too far. The bike does not fit me and we can't make it fit.
I'm going to take it to a shop that will sell it on consignment. I'm not shopping for a new bike right now, because I really can't afford anything nice, and I am not excited about paying nearly $2K for an aluminum bike, as I would have to do with a Terry. I am just going to cut my losses and try to learn to love my mountain bike.
Thank you, everybody, for your help.