> As I am an employee now, as are many of my brahmin friends, are we shudras now? If I start teaching the holy books, do I become a brahmin?

Yes that is right, if you become a teacher, lawyer, guru or advisor, you become a brahmin as intended. You need to be guided by the guidelines meant for a brahmin, do not be driven by wealth or power or accumulation of land.

Birth based assignment of varna has always been debated as wrong interpretation most famously in the Mahabaratha.

Unfortunately, it is human nature to assign birth based privileges. Most famously by projecting Rahul Gandhi as the only viable opposition leader, by birth privileges.

Ironic considering Modi the son of a tea seller is demonised.