I weighed Gwen at the health unit today and she was 10 pounds, 5.4 ounces. Since their scale and Lillian's differ, to compare apples to apples you have to look at her last weight from that facility, which was last Thursday at 9 pounds, 6.5 ounces. So very nearly a pound in 6 days. Clearly the formula is working.
The nurse I saw today confirmed that there is nothing magical about formula over breastmilk, and heartily agreed that I could "top-up" with breastmilk if that was what I chose to do. So for now it's breastmilk top-up when we're home, formula when we're out (because you can mix formula on the fly and not have to worry about keeping it cool). Soon I'll be lying to old drive-by noseypokes just like Amber.
There is a whole thing going on with the stoopid mystery bacteria but it annoys me and bores me so much that I can't imagine you would want to read about it. Just know that I am frazzled and frustrated and mostly not thinking about it, and I'll let you know what's up as soon as I do.