I got some Nutri-Cal nutritional supplement (in a tube - from the pet store)when we brought Lexi home at almost 11 weeks. If I don't feel she has eaten enough, I feed her some of this according to directions & she is crazy about it!
It s/l you are doing everything you can think of & receiving great advice for your special situation. BTW, congratulations! I feel exactly the same way you do - loving having a puppy nestled in my arms & lap but forgot just how much work it truly is but SO worth it too!