a) A PAL frame consist of 2 fields, even/odd as you've noted. It sounds like your capture is not capturing and integrating one of the fields correctly. Are you handling the Field signal correctly
b) When you capture a line of video are you starting at the beginning of active video. By my calculations it should be 144-12 = 132 samples after the falling edge of Hsync. (assuming a 13.5MHz sample rate)