1. I
LOVE Maisie! It's one of the sweetest, happiest names I can think of.
2. I prefer
Maisie. I guess it just looks more correct to me, since I'd never seen Maisy until your post.
3. I can;t really say without knowing what your surname is. I don't think
Maisie would sound too out of place on any ethnicity, though.
4. Sure.
5.
Maisie Rose sounds better but I find
Rose to be the most bland mn ever. I'd recommend something else.