I'm a teacher so I'm partial to "regular" names, and I do not like Erasmus at all. I like Xander better than Sander, although I think Xander is pronounced "Zander" and "Sander" is with an S.
I think Evan is a boy's name and most people will think your baby is a boy
if you go with it for a girl.
If it were me... I would choose one of your middle names for a first name and save "Erasmus" "Sander" and "Evan" for middle names.
But in the end, this is YOUR baby and like I always say--- name him or her what YOU love. This is why we don't tell people the names we have chosen till after the baby's born. I have 2 friends, one who named her kid Dewey (actually met her on here), and the other who named her kid Korbin. I didn't like either of the names at first (but never said so of course) but after the kids were born and I got to see them and learn their personalities, they both totally grew into the names and I can't imagine them being named anything else. Good luck and welcome to tbc.