I have an Origin 20 head with a 4x12 slant cab. I also have a Behringer interface for recording. 

I have 3 questions.,...

1) Can I connect the DI Out to my interface?

2) Should I use a speaker or instrument cable?

3) I have attempted to connect to both a PA amp and to my interface and get an electric hum. I can still hear my instrument but the hum makes it unusable for recording purposes. Is there a way to eliminate this hum?