If i see a player limp many time, I will raise him much and float much as well in postflop.

And if in live game, I usually open 3bb in early positon and 2.5bb in btn.

usually open between 4x and 5x in ep.. also, opening up ur range in soft games is def good

It really depends on how weak the players are.  Your comfort level of playing post flop is what determines how wide you can open.  I don't think your open size matters as much as your post flop play.  You can open wider with a 3x strategy, as your opponents will most likely defend a lot more hands.  However, you have to be prepared to play a lot of pots oop and be able to exploit weak players with capped ranges.

When stacks are deep and a fish limps, I usually iso with most suited hands.  I limp behind some weaker connectors, and sometimes open to 3x with lower pairs just to build pot for when I hit sets, it also gives you the initiative, as in it allows you to check/cbet and get to see 3 streets almost always.  You can really push your edge to the max by just being involved in as many pots with the fish as possible, but be careful to not get too confident and make sure you post-flop play is solid, other wise you might start spewing...  

Good question. I think having a solid starting range like 89+ suited connectors are fine, all pairs and Broadway cards. The more money would be made by attacking weak limper from early position by isolating then with a big raise 5 times for value and semi-bluff from late to mid position. Open too wide can have its disadvantages because we could lose the edge we have over the players for playing too loose and out of position. I think exploiting weak players and fish individually is a way to go. Raising 5 times big is absolutely fine because you know fish are going to limp call any way and you put more money in the pot in position for value and exploitation against a weak player.