I can tell you how I get the chest.
First go strait up till you get to the block step one block right drop a bomb. Then go strait back down stop till they get close and set another bomb. They should be all bunched up and step into the bomb. You can then go right up and run left to the chest about grab everything. They will be all coming up that side you can then run left to the wall. wait till they all get real close. Set another bomb run strait down and go right and get back out.
The trick is to get them to bunch together and step on the bombs all at one time. You can't do that with the very first bomb but it gets the ball rolling and helps bunch them up.
The second bomb delay as much as you can set the bomb step one step right. wait there till they hit the bomb. Then run.