2A.) As for making the boat more vulnerable, what do you mean? Like now the boat can blow up if it takes too many hits in areas where bullet hits would be redundant in real life?
2B.) As for real-life German PT Boat models, I remember there being on in either Sniper Elite 3 or 4. Perhaps it can be imported like you did with the tanks?
2C.) That tower...
3.) As For Germany 1, I think those posts look out-of-place myself in that particular spot, close to the door as they are. I think the German mansion owner's wife would find them too distasteful. Bear in mind that this is deep inside Germany, not France like in that MoH mission. I think the huts would be better near the entrance to the Maze, as well as near the gate.
4A.) As for Norway 2, I was thinking; Hidden & Dangerous 2 has two different models for music/news radios. Perhaps one of them can be imported, to be used instead of the military radio you're currently using for the music?
4B.) I still think that the man in charge of the facility of Norway should be a high-ranking officer as it originally was, rather than the basic soldier or low-ranking officer you have him being. And I think he should possess the key to the locked laboratory.