1. That all depends on the grammatical context. The two are not interchangeable. How is it with you? It's the same with me. How did he do it? The same as me. A. Whenever I talk to Jack he gets irritable. B. It's the same WITH me. Whenever I talk to Jack he gets irritable, too. I guess he has a chip on his shoulder or something. 2. Two different expressions. How does he look now? The same as before. or...The same, just like before. 3. "Ever since" is usually used in the negative, i.e not ever Ever since he got married, he hasn't been a happy man. = He has never been happy during that time.

Your examples #1 & #3 are indeed alternate ways of saying the same thing. However, in #2, the correct way to say this is "the same as before." Using "like" is bad English, but unfortunately it has become common among many native speakers.

"As" is the preposition that goes with "the same". Stick with this rule and you'll be fine. Using "with/like" does happen, but it's either a case of carelessness or it begins a new part for the sentence. eg. "my sister feels the same with me" reads as "my sister feels the same, when she is with me". "Ever" can be understood as "at any time". When paired with "since" (ever since...), it emphasises the action, starting from the time when "since" begins.