How to tell my friend I like him even when he has a gf? Without messing things up.

Code names: Jane and Joe.
Ok, our dads are friends And go hunting together and sometimes leaves me at Joes house for long periods of time. He has so much energy because he's diabetic and runs high, he's funny, and we both have red hair. But his girlfriend hates me and I think is planning to do something but whatever. One day I was over at Joes house for a dinner and his little cousin told me I was ugly, and Joe and his gf both said I was beautiful, Joe having said it first. My problem is I can't tell if he's flirting or just an all-around sweet guy. And on New Year's Eve Joe was supposed to go to his gfs house, but instead he came to mine and made her ANGRY . Then out of pure curiosity I asked if he jerks off because he's always pretending to and is always pretending to hump things. Should I tell him how I feel?