SPOILERS!BF, you are totally right about the smoke / swimming pool scene. Very strange.
The forest scene: I still think it was the intention of the movie makers to give the impression that Marc was leading Kay's hand in a certain direction, but you are right again about the left/right hand. Probably this scene is shot in parts and from different sides and I think this happens all the time when making movies, without the viewers noticing this.
Good that you did. Ik could see this a thousend times without noticing.
However, of course you could be right and the intention is diffent.
Curious what others will think when they watched the movie.
It's a little detail but in my opinion important how to interpret. It's quite a difference: Kay puts his hand in Marc's pants because Marc "asked" him to or Kay puts his hand in Marc's pants despite Marc tried to push him away.
Then another thing. I was wondering why Marc was back in the training camp. But could it be possible that he was doing that run test at that moment (at the end of the movie)?
One other thing about the scene in Kay's apartment. After Kay told Marc he loved him, they wrapped their arms around each other and kissed. At a certain moment Marc put's his tongue in Kay's mouth and to me it looked like if Max withdrew his head, as if he was shocked a little (like: hey fellow, take it easy). Curious what you think.
About Max: on youtube I found a nice video. Is from a few years ago, but I liked it anyway. You see pieces of several movies and interviews and all comments are in English. When you search for Kino the German film magazin you will find it. From 14.20 it's about babyface max

.