DC is not too small to become a state. Its population is larger than Vermont and Wyoming and getting close to Alaska.
If DC becomes a state, yes it would it have two senators, just like every other state.
Washington DC has too much power now? Residents of Washington DC are not the ones in power. In fact, having no voting representation in Congress means they have much less power than other U.S. citizens. The ones in power in Washington DC are from states. They may live in DC — mostly temporarily — but they pay taxes to their states.