Dick was a college student, and Barbara was in congress as you said. In
Batman Family Issue #7, Dick actually says "she's got to be seven years older [than him]"
They were not an item (in the actual 1970s), though I wouldn't have minded it. They did a good bit of teaming up in the Batman Family comics. He had a thing for her, but they never actually dated. She did kiss him once, but that was just to shock him into silence (fanservice). I actually do ship them (well, the mature, emotionally healthy versions of them I like) , but I very much do not like a relationship being retconned into their earlier history at all. In terms of publication order, they never dated until the Dixon was writing them in the late '90s/early '00s, so far as I'm aware. I'm pretty sure I've read all Barbara's pre-COIE appearances, but am not absolutely positive.
Ah, comic book references to time. Actually, a few months (real time) before he went to college, Dick was described as a junior in high school.
Someone on this site (so sorry that I cannot recall who), posted
this link with references to ages. I'm do not perceive the Earth 2 and golden age being the same and this does handwave the requirement for Barbara to be 25 to be in congress, even though that's in the Constitution. But there are a lot of good citations there, anyway.