OP, I understand the need for some restricted diets because I, too, have a restricted diet and part of my required preparation for adoption was to learn to cook meet. It still makes me gag.
However, in the context I mentioned it I meant that if you / DP haven't lost weight before placement then your child will be in an environment where calorie counting and weigh-ins at WWs will be the norm (although getting to a WW meeting may be no more than a dream when small person arrives) and a child who has probably suffered neglect / food deprivation / almost certainly expresses emotional need and want and control via food should live in a home where food isn't an issue: it's just what you eat to give you energy and enjoy the sociable time around the table. Perhaps think how you could make sure that if you are both on calorie controlled diets you wouldn't let the philosophy of calorie counting rub off on the child.
And why not gain a bit of muscle? Lift a few light weights. Muscle has a higher metabolic rate than fat so the weight will come off more quickly if you have more muscle.
I am writing from an informed position on weight control, health, medical issues etc. but not from the emotional aspect. Italian is your woman for that. She explained the issues around self-esteem, comfort and such to me really well because I didn't get it. A mentor like Italian (not volunteering you hun) might be just what you and DP need.
Please do remember that the adoption process is full of seemingly ludicrous hurdles but the WHOLE process is child centred and, to adopt a child, that has to be the frame of reference of your life.
Good luck on your journey.