1. My partner has been ok, not for lack of trying bless him, but he's a naturally messy person which obviously sends my OCD a-raging! I've only told my mum and sister in my family, and they've generally been supportive. I think my sister also has OCD but it's undiagnosed. I'm quite open about it with work colleagues, but because I work in Neuroscience/Psychology, most people are very familiar with mental health generally and so it's less stigmatised/I don't have to explain myself.
2. As far as I'm aware, there is huge overlap between anxiety disorders and ASD generally. As xudo said, it's really hard to work out what came first / what influences what. I'm self-diagnosed as an aspie, and I'm sure it makes my OCD worse (or vice versa...). E.g. my need for order and routine are super-intense/compunded because it comes from "two sources" in a way (both ASD and OCD).
3. My OCD has actually generally got better over time, with me learning new coping methods. CBT / mindfulness have been amazingly helpful. Some of my routines have morphed to be different, mostly they're a bit shorter and less involved now. But it was much worse when I was younger (see below).
4. Yes, I think my OCD developed around the age of 8 or 9... not sure exactly. But I used to have thoughts like "unless you do X routine, your family will get hurt", or whatever variation, constantly. I got better at ignoring this as irrational over time, but it took ages.