I'm sure that our ideas of nightlife differ dramatically, but there are lots of film festivals, a jazz festival, Blues on the Waterfront, concerts, etc., year round in this city. If you can't afford them, then that's one thing, but they are there nonetheless. The pubs all seem to be jammed, particularly on the weekends.
I also don't know what you mean by culture. Portland has a thriving art community and many galleries. There are artists here that are known worldwide. There are endless venues for music, everything from symphonies to one-man gigs, and several jazz clubs, concerts in the parks, at the zoo, etc. There's also the Portland Art Museum which has rotating displays all through the year on loan from other museums.
Good luck finding somewhere else that suits you better. I've lived here, in Washington state, Alaska, Washington DC, Virginia, Southern California, Idaho and Massachusetts, and traveled a good number of the larger cities in this country. I've also lived overseas for many years. Portland compares favorably with most of them. From what you've said, I don't think you'll be happy anywhere.