Sorry friend, I am here only occationally (vacations etc) and I am really not a frequent player. I do not have time to play-test in any other way then in TripleA. You can find me there from time to time as Granada but I cannot host now.
Regarding the Russian sub, you are correct. I have not inculded it because it survives only if you decide to submerge it during the R1 attack of German sub, fig and bomb on SZ2 before the fight. But it further diminishes the likelihood of the success in this particular battle. You cannot take the potential hit by the sub on it, which is good because it gives your battleship good chance to get at least one plane. If you keep the Russian sub in the fight the likelihood it would survive is about 60 %.
If you include the sub to the R2 battle calculations in the SZ8, you are correct that it changes the odds for the defender in case of 2subs plus four planes on the German side. In case attacker has built a bomber R1 and still has three figs to hit you, the odds for him to win remain 66% with 1,7 units left.
The fact is that the Germans must build a bomber R1 if they want keep the likelihood of Allies merging in SZ 8 with stronger fleet under 50%. R2 you really can prevent them to merge there and R3 you cannot perhaps prevent them to land some troops somewhere. You are perhaps right in that respect.
Still the question whether the Germans will not get their planes to the point when they will sink some of your fleets especially if you decide to split it will be omnipresent and the dynamics of the sea battles in the Atlantic have definitely changed in their favour.