I’m not sure what you plan to gain from the DD that helps the Russians.
Mostly, the first turn the germans attack the Russians they don’t need the fighters, so they are free to sink ships. One more DD doesn’t change that.
The germans can transport men north unimpeded until they attack, so you aren’t stopping any German reinforcements.
Maybe I’m a poor German player, but i don’t focus on the Baltic. Just go overland until Russia is destroyed.