Reading 捻る: when is it ねじる or ひねる?

Question

How can I tell whether 捻る is read as ひねる (P. ・ N.C.) or ねじる (P. ・ N.C.)?

I assume the answer is "based on which verb is appropriate", so I've been trying to learn the difference between them. Based on the links above, here's what I've got so far:

1. They both generally refer to twisting. There are cases where it could be read either way, because the meanings overlap:　「体を捻る・水道の栓を捻る・足を捻った」
2. When you put a lot of force into twisting, it's ねじる. So you use ねじる when you're opening a bottle by (forcibly) twisting the cap off:　「びんのふたをねじって開ける」
3. If you're twisting something with your fingers or fingertips, you use ひねる: 「ひげをひねる・スイッチをひねる・鶏をひねる」
4. Metaphoric uses appear to use ひねる: 「頭をひねる・ひねった質問」

Does this seem correct?

Answer 1

One of the dictionary entries the OP cited elaborates on the difference:

[用法]ねじる・[用法]ひねる――「体をねじる（ひねる）」「水道の栓をねじる（ひねる）」など、ひねって回すの意では相通じて用いられる。◇力を入れて回すときは「ねじる」、指先で軽く回すようなときは「ひねる」と使い分けることがある。「びんのふたをねじって開ける」「スイッチをひねる」◇「転んだはずみに足首をひねって痛めた」「腰をひねって医者にかかる」などでは「ねじる」を用いない。◇「ひねる」の方が意味の範囲が広い。「頭をひねる」「首をひねる」「俳句をひねる」「強敵にあっさりひねられた」などの使い方は「ねじる」にはない。◇類似の語「よじる」も「腹をよじって笑う」など、使い方は限られている。

In short, (1) they both mean the same when used for "twisting" something; (2) If the twisting is done with force, ねじる can be more suitable over ひねる; (3) In some cases only ひねる is used, e.g., 足首をひねる, 腰をひねる; (4) ひねる has a wider variety of meaning, e.g., 俳句をひねる (I create a haiku poem); (5) A similar word よじる sees even more limited usage, e.g., 腹をよじって笑う.

So basically your understanding is fine.

Answer 2

ひねる is to twist, ねじる is to twist (into a coil-like, or with the coil-like shape as an implicit objective). And I guess the amount of strength used is implied because generally more force is required to twist it into a coil shape.

The (poorly drawn) picture represents my interpretation of the difference: