In general, the only time it's ever worthwhile to do this is to research ice/volcanic colonization techs and then scuttle the labs.  A few Advent players will build a temple of communion while they're at it, but otherwise if you're going to pick up anything more the labs shouldn't be scuttled.

That depends.  You basically pay for 75% of the cost of the structure (50% if you've got the Vasari 1st level tech researched) to make the move, and that may be a little on the costly side.  In most cases, it's a pinch cheaper to buy a logistics upgrade.  I'd be more inclined to avoid filling the logistics space in the first place rather than trying to clear it out later.

Generally you don't need logistics space at your homeworld.  They rarely have enough outgoing lanes for refineries to be a must-have, you only really need one trade port (and that's IF your longest trade route goes through your homeworld) and sometimes they're a good place for culture generators.  I've used my homeworld for nothing but lab space before; sometimes the HW really is good for nothing more than being a tax/extractor farm.

Instincts of a civilization player.  I was there, myself. 

Always try to envision how you intend to use your logistics later on.  This is most difficult at the very start of the game when you've only scouted 2 or 3 jumps but need to put up your first pair of labs.  Obviously you just don't have the information to make those calls yet, so it's a bit of a gamble at this point.  After that, you should have a general idea of where you need to put trade ports, culture generators, and factories.  With that in mind, you can spread your labs out while keeping the necessary slots open.