I agree with you. There is plenty of reason to believe Mary had other children the normal way, and only contortionistic speculation that she didn’t.
There is nothing wrong with Mary and Joseph procreating as is normal.
Exactly. There is nothing wrong or unbiblical about it. Her main purpose for God was pretty much over and her and Joseph - being normal, mortal humans - could go on doing what humans do
It's like using the vessels of the Temple for profane winebibbing (didn't one of the pagan conquerors of Jerusalem do that?) or using the Ark of the Covenant for a cheese cupboard. Not that there's anything wrong with wine and cheese. But it's the desecration of something intimately consecrated to the Lord, for common use; which is to say, a sacrilege.