Matt, read
this explanation about the 28 day rule and why you have 28 days.
1. Yes you can, your first entry shouldn't be a problem afaik. Although you are not sticking to the reason you got the visa, you're also a non-visa national, so I don't think there should be much problem. If you go this route, don't worry about it.
2. I would say no - that's just personal opinion. You would be entering as a visitor, not really to stay there to become resident. When you fill in your ILR application in 5 years time, do you really want to "lie" on there if you only actually moved there in April.
That said, read my post and the concern about extensions (all speculation though).
I am not sure why you would have chosen 6 February if you could only leave later.