Whew, lots of questions here. Start at the top:
1. When figuring out where to price your figs, ALWAYS look at the sold prices, not the list prices. You may be seeing significant differences in list prices between the two portals because listings on BL can remain a lot longer than listings on eBay. On eBay, I believe the longest a BIN listing can run is 30 days, so there's more incentive to set a reasonable price. Anything will sell if it's priced correctly, even if there's 250 other listings of the same fig.
2. Sell whole used sets w/ minifigs, or part out figs and sell sets separately - like everything, it depends. Unless you have some killer, unique figs in some of these, I don't know if it's worth your time to part them out from your set.
3. Bricklink - People buy from Bricklink all the time, and these sets are new enough that there should be some sold listings on the figs. I just made a BL purchase last night! Signing up for a store is free, so there's no risk there. I would say that you will likely get a sale faster on eBay, but it depends on how competitively you price your listings.
4. Random figs - bulk or part out? If there are any special or even decent figs, take these out and sell them separately. These would include troops of any kind and/or licensed figs of any kind. You could even consider listing any fig with significant detailed printing if you wanted to spend the time. I would consider selling the rest of the random figs in bulk.
3. Desirability of bulk lots - Bulk lots do often sell, but you will likely get more return on your bulk lots by parting them out. The downside to this is it will take a LOT more time to post these lots, and a LOT more time to sell these lots. If you've got the time, then consider parting out your bulk lots by color/brick type. Some members who do this often and successfully do this in front of the TV as part of their before-bed relaxation routine...
Hope this helps a little-