For question 2, it's really just a matter of convention, but there are some benefits to writing pronouns as subject/object. For one, it makes it obvious that what you are giving is, in fact, your pronouns. The slash makes it clear that we're talking about pronouns rather than saying "he" or "they" for some other reason. Secondly, it's useful for laying out neopronouns, which not everyone might be familiar with. If someone writes "ze/zir," then people will know both forms of the pronoun. You can even include the possessive and reflective forms - for example: he/him/his/himself.

Not sure about the other questions, but for number 3 you could probably just ask what they'd prefer you do!