I think you are getting some great, honest pricing feedback from your customers here. I wish my customers would give me this kind of direct feedback on pricing.
If I am reading your response correctly, you probably make in the ballpark of $40-45 per user on ad revenue. So really do need $50/user, if you aren't going to show ads. Just a guess . . .
Sounds like you have a tier of users who would pay for a bolded name, access to religious and political categories and all the rest, but don't care about the ads. Introduce a $20-$25/yr level that includes all the benefits of premium, but still includes the ads. And all those things don't cost you a cent Then you get the ad revenue + $25/yr from that crowd. I know I'd pay for the $25/yr tier!