Because it sounds repetitive and lacks professional nuance.
Only if they explicitly ask you to ('Putem să ne tutuim'). In most Romanian companies, formality is the default.
Not inherently, but it can sound patronizing if used by a younger person to an older person. It's safer to stick to 'dumneavoastră'.
Yes, but it's becoming less common in cities. It's mostly used by older people or in rural areas to show a 'middle' level of respect.
This is called clitic doubling. Because you moved the object 'Cartea' to the front, Romanian requires a 'placeholder' pronoun ('o') before or after the verb to maintain grammatical balance.
It's a marker for the subjunctive mood, used for wishes and commands.
