여기에서의 '놓이다'도 put 의 의미로 사용되었다고 생각하셔도 돼요. 무엇이 어디에 놓일 때는 그것이 놓이는 장소, 상황, 혹은 시간이 필요하기 때문에 '-에'가 앞에 붙는답니다.

It can be used in various situation and it refers to many different feelings. It can be - 'something is not right', 'I think it is odd', 'I am suspicious of it', 'It is weird', etc. One thing I can clearly explain is, it is generally used to express your negative feeling.

It seems like it it newly made word on the internet. Even I don't know what it means with this one word. But I am sure I can tell you what it means if I get the whole conversation or context.

There are no grammatical mistakes to use both. But in normal conversation, it sounds nicer to use "내가 배고파서" rather than use "내가 배고프니까". Because if you use "내가 배고프니까", sometimes it can be misunderstood by your friend that you don't care whether they want to eat or not. On the contrary, if you use "내가 배고파서", then it means you want to eat because you are hungry, but you are still giving them room to say how they feel about it.