Hi Shinobi, welcome to SH5,
I feel your pain, I recently came back to SH5 (and subs) after being frustrated in the past by modsoup, CTD ect....
...to find this little gem which will fullfill your sub needs of question #3, trust me! Megamod The Steel Wolves:
http://www.subsim.com/radioroom/showthread.php?t=210703
Step by step, noob proof guidance, awsome range of mods, and above all, stable gameplay!
The autor, vdr1981 (Vecko), also strives for maximum reality.
Sobers Megamod and Sjizzelz Megamod are also popular, requiring more commitment/time to manually downloding the mods. Then again, you have more flexibility on which mods to activate.
As for Uplay, I still have the annoying start screen, but I disabled online mode.
Maybe more is possible, dunno.
Single player campaigns via Open Horizon II (integrated in The Steel Wolves!)
Again, I recommend opening your tonnage via The Steel Wolves.
Cheers, Trebb.
NB You will have to do some digging in the forums, on how to start a campaign;
http://www.subsim.com/radioroom/showthread.php?t=192374
real navigation, ect. Read Sobers campaign notes after installing and configuring and then proceed futher...