OK...
1 - if you're under 140kts then with 3k+ visibility I think it is legal. I guess the "I think" means that yes, the rules can be confusing, but the they are probably fine in most conditions - I think the confusion is for conditions far below what most PPLs or PPL/IMCs would fly in.
2 - Departure in these conditions is reasonable with an IR, bit daft with just an IMC (cloud conditions are well below the recommended minima for an IMC holder). I'm assuming that there's no icing or the aeroplane can cope with it. En route, well there's not going to be very much in the way of traffic flying in uncontrolled airspace in that weather and it's a big sky. I'd guess that the chances of a mid-air are much lower than other failures that could spoil your day (although I have no data to substantiate that).
3 - Dunno, ISTR that route charges could be involved.