That is what tanks are for.
and if SZ6 is not working, move to 7.
The point is, if you cede control of the Atlantic by just sitting in the baltic, then you probably ARE wating your money on a Baltic AC.
Build your fleet, then eitehr use it to take out a few units, prevent early landings in Norway and Africa.
But if you are just using it to be just a guardian of Germany and Eastern coasts (which is an acceptible use of that fleet), then don;t complain about the Allies building their fleets up outside your range. If you go purely defensive with the Baltic Fleet, that is what the allies are going to do. And when they are done, your fleet is sunk. That is jsut th way it works.
Either use teh fleet to protect Germany and Eastern while you drive hard on Russia with all you’ve got and deal with the Allied landing swhen they start, or use that fleet and challenge the Atlantic with naval and air.
But don’t complain because the Allies see which way you are going and adjust their strat accordingly.