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.