I don't know, it sounds to me like your sitbones just haven't toughened up enough yet. If the only pain you were having on the 155 Lithia was in the sitbones - where all the other narrower saddles chafed your girly parts - then it really sounds like it's probably a good saddle for you. Some sitbone pain is to be expected for a new or returning rider.
How many miles did you put on the Lithia before it got painful? Did it just feel like bruising? How long before the pain went away?
When you say it's your first new road bike in 15 years, have you been riding another type of bike all along? If so, what kind of saddle is on your other bike(s)? Or have you not been riding at all up until now? Was that 7-10 miles a very short ride for you, or a long one, or average?
ETA: you may still need to tweak saddle tilt even after a very good professional fitting. For one thing, a tilt difference of just one degree can make a huge difference in comfort. (And if you don't have a micro-adjustable seatpost, you can shim it with a little piece of metal cut from a beer can.) For another thing... well, they don't measure you THERE.
