It is ok, but you might get some strange looks. :) If you want to avoid that, use kamarád/kamarádka. Kámoš/kámoška is more like 'buddy.'

It is OK in this case. The word "přítel[kyně]" implies a closer and more trustful relationship than "kamarád[ka]". The sentence sounds very earnest, like something you would say after your friend would offer you help in a difficult time.

When speaking about boyfriends and girlfriends, possessive pronouns are usually present ("můj přítel", "moje přítelkyně").

Since the sentence says they're friends, they probably use "vy" mutually. So I would interpret it as a professional relationship.