Why is it זהו instead of simply זה?
could be both
There's no difference in meaning?
no difference :)
It is the same..
In my opinion it should be "סלח לי" instad of "סליחה"
Well, סְלַח לִי would be the more literal translation, but סְלִיחָה is the more common way to excuse oneself.
Could be used ויכוח here?
The correct translation of ויכוח to English is argument in my opinion. We (Hebrew speakers) usually translate דיון to discussion. So the translation offered by DL is correct, although the meaning of both words is quite similar.