I did almost the very same thing. I started my Preop a month before surgery to get a head start. I went strict with 5 shakes daily for 2 weeks before surgery. By day 4, I was back having a light meal at night.
Grilled chicken over salad day 5, grilled chicken sauteed with broccoli rabe the next night. I called my doctor and told him and he said I'll be ok. He said the biggest thing was that I didnt have any starches, no added fats, and no sugar.
He knows I dropped 25 pounds the last 4 weeks so the light meal at night wasnt going to enlarge my liver again. But he would prefer I go shakes only the last 5 days.
So dont worry about a steak one night. I think you dropping 20+ pounds shows that you've been doing just fine.