Advisor gives me no choice on research topics - should I tell him my real feeling?
You should clearly and explicitly state to your supervisor what you want to work on, and realise that this may not be possible in their team.
Once your supervisor knows what you want, they may be able to help you find a different supervisor to collaborate with during the remainder of your PhD, if the proposed research is not possible in your current group.
Of course, there is the possibility that your supervisor is right: maybe the theoretical problems you are proposing to work on are not publishable, or too difficult to complete during the time you have. This is something you can talk about with them. Maybe it is possible to work on your topic of interest, if you can convince them that it can be completed in time, that it is publishable, and preferably related to the current research topics of the team.