Why is shi n so hellbent on keeping his feelings hidden? Isnt he in love as well?

It's becuz my baby shin serves the Kingdom and he wants the best for wolfgang even if that means hiding his own desires.

I hate him for being to self less （￣へ￣）

shin takes responsibility in putting wolfgang on the throne which is why he is hell-bent in making him a great ruler. it's only rational that he doesn't let his feelings affect his actions. of course, since they're in a relationship (somewhat) he should be more expressive but when it comes to palace affairs his attitude is just practicality.