put the case back on, turn left (couter-clockwise) until the back is in the grooves, and then tighten clockwise. that works best to make sure its on correctly. i always use the sticky ball, and it works great
Sounds like you should send it back and have it the movement swapped or get a replacement. If the problem is severe enough to loose a minute every five minutes, then it's not something you could just fix easily. if you dont want to send it back, you could replace the movement yourself, but that would cost more.
If you're looking for aftermarket straps, there are dozens of great strap makers, including a number on this and other watch forums. They range from $30 - $300, in all different styles and sizes.