You can transplant while it's flowering. It's only harmful if you damage the roots (or the plant) in some way, so be very careful if you decide to do so.

It still has potential, but will need much more light. Maybe (at least) twice of that what you are using now.

What kind of lights are you using?

One reason it's so tall and skinny could be that it's reaching for more light. If you are using fluoro's or CFLs, they should be 1-3 inches from the plant, and situated all around it, not just above.

All in all, a good first grow so far :greenthumb: