Difference between 坏 and 破 Looking for some concrete answers on the difference between 坏 and 破

From what I have been able to understand:

坏


bad: as in 坏人 (bad person) or 鱼坏了 (rotten food)
broken: as in 手机坏了 (broken mobile phone,) or 腿坏了 (a broken leg)


破


ripped: as in 这张纸破了 (ripped piece of paper)
worn out: as in 鞋破了 (worn out shoes)
broken: as in 手机破了 (broken mobile phone,) but not a broken leg


My issue is the overlap, unless I'm wrong. It looks to me to be something like a venn diagram (http://maass.nyu.edu/images/venn.jpg) where broken is shared by both words, and there are other meanings that belong only to each word. Is this right?
“坏” is a very general word meaning something "useless", but what makes the thing "坏了" has many reasons, and “破了” is one of them, so when something's state is “破了”, you can also say something is “坏了”；However “破” means something is broken or has cracks. So when you describe something that is useless because of inner reasons such as quality, but it still looks nice in its aspect, “破了” is no longer used.

Try to compare the two sentences：

1）这热水袋破了（The warm-water bag is broken, maybe is of cracks by falling down onto the ground）.

2）这热水袋坏了（The phone is useless, maybe it doesn't keep warm anymore but NOT of cracks）.