No, Khairnar is not Brahmin Surname. It is Marathi Surname.
Yes Vaidya is Marathi Brahmin surname, but found in other castes too
No, it is a Maratha surname (Kshatriya).
Yes.
Yes. This some Deshastha Marathi brahmins hold surname Bhandari
Deshastha Brahmin
Deshastha Brahmin
No, it is a Bania/Vani surname, meaning it is a Vaishya surname.
The Surname Tatwawadi in Marathi are Hindu Brahmin (Deshastha).
Marathi Surname "Keskar" belongs to Dhangar caste as well as Brahmin caste.
Saraswat Brahmin
Kokanastha Brahmin