A: You should ask him out in person, doesn't necessarily need to be for a date, just lunch or something. This will help build your confidence (very important), and it sounds like you can count on him saying yes so there isn't much risk involved.
A: I think a girl that has that type of approach typically comes off as confident, which is a good thing...but it will all depend on what a guy is interested in. Just be yourself, and be careful not to joke at the expense of others, which will come across as petty.