Considering *roughly* where your saddle is supposed to be, you'd probably want a stem that's about 60 or 70mm long. Does that sound accurate?
You can also try mounting it upside down (eg. +7° rise instead of -7° drop) to get the handle bars a little bit higher. You should be able to get away with your 80mm stem by doing this, at least for now.
Why don't you try to move that saddle about 2cm back, install the 80mm stem, then update us with the results and maybe post a pic?