re: How old is Gollum supposed to be?

They were river hobbits I think. More inclined for adventure and stuff.

Sam can't swim, I don't know if any of the hobbits can swim, but Smeagol and his buddy (forgetting the name) fished on boats and went swimming.

Hobbits in the shire seemingly farmed and did townie stuff all the time. Bilbo was kind of an oddball in that he welcomed adventure.

As far as what other events Gollum was around for, I'm not really sure.