Manchester is lovely
I'm just outside of it but I'm still a token Manc, Annie will give a better perspective of those questions tho. But nightlife has always been lively, some decent clubs and bars about, you'll get the odd dickhead but it's expected. Just like you'll get the odd dickhead who isn't culturally accepting but it's definitely diverse, it's one of the largest cities in the UK, it's to be expected
Depends what sort of activities you are into, has decent shopping centres, museums etc.