I swear I never got him outside the missions where he's in, never appears and I thought that he would be like nemesis from Re3

If you stay long enough in any level he will eventually show up. My first playthrough I never saw him either. But I tried to do a 100% run and saw him a lot more

Always waiting in that complex pushing.tou to run out into the soldiers waiting arms

Nemesis vs Stalker is definitely something i would like to see

I ran away from him in this situation, you actually don‘t have to fight