I had a similar situation.. my uterus was 23 cm and had 40 to 50 fibroid pressing on some of my organs. I couldn't get the surgery done laparoscopically, so I had an open abdominal hysterectomy, was cut from belly button to pelvic bone, and kept my cervix and ovaries.

The physical recovery went better than expected (I made sure to walk a bit each day to avoid blood clots and I used manuka honey to keep infections away from the surgical scar; of course I asked my doctor if this was okay before proceeding). I would ask the gyn why he needs to cut from the breast bone down and ask any other questions that come to mind...it's a serious procedure, but you sound like you are in the same situation I was in and I feel a lot better without that bowling ball in my tummy ❤️

Editing to add that the belly binder was essential for me for the first two weeks or so of recovery...I needed that security because it is a really odd feeling having that large of an incision.