The proletariat is wage-laborers (those who rent labor to capitalist, rather than applying their labor to their own capital—as the petite bourgeoisie do—or renting others labor to apply to their capital—as the haut borgeoisie do), not exclusively manual laborers.
Rubbish. The status of being a proletarian has nothing to do with in what form the labour is expended. Neither Marx nor pre-Marxist Socialists make any specific mention of manual labour. But if you really want to go this way, a growing number of the student population in Europe are turning to manual labour (Uber and Deliveroo).
Proletarians are and since their emergence the vast majority of the working population.
We have skipped this one too if you didn't notice. In most of the world, proletariat (manual laborers) are a niche.