Your interpretation is correct I think. To me, it means this is Steve being his most typical self. In the UK (maybe in other places too), we often say 'classic Steve'. It means that the thing Steve just did or said is absolutely typical of him. However, 'classic Steve' is usually an affectionate thing to say. 'Peak Steve' seems to be said disapprovingly here. Is this from a TV show? Which one?

Hi mate. The phrase "it's peak" is slang. Barely ever used and not something I've heard someone use in a long time. It means something along the lines of "bad luck" or "a bad situation." I'm not sure what learning tool you're using that included this but it's actually kind of strange they would use this phrase. I can also say that if you used this in a native English speaking country a lot of people wouldn't even know what you meant lol. Hope this helped :)