I cannot abide affairs. Cannot understand how you can do that to someone you love. But to my mind is the party who had the affair - not the one who did the tempting - is the one in the wrong (although I can't see how you can be attracted to someone willing to do that so the tempter is pretty stupid!).
Sid is going to be blamed, at least by some. Not fair.
Please dump him Zara. And don't turn alcoholic - even though that is clearly what's planned. You were in the wrong with Sid but Danial really is a tosser.