頭の中は恥辱と奇妙な解放感に混乱した。ともすると恥辱と刺激だけが意識を占めてしまいそうになる。
彼の掌から甘い痺れが沁みこんで来て、ともすれば腰が抜けそうになる。
呼吸を整えることで、ともすれば崩れそうになる自尊心を平静に保とうとした。
Regarding these examples, it seems "as a result," is more appropriate than "a tendency to ~, prone to ~" for the uses of ともすれば・ともすると. The clauses after ともすれば・ともすると feel much more like a outcome due to the actions in the first clause than a long held habit.
even with 大辞林 I still only get どうかすると。ややもすると。ともすれば as definitions.
ともすれば is an adverb that adds the nuance of "possibly", "if things go bad", "if we're unlucky", "depending on the situation", etc. I don't know where you saw "as a result", but that's not what this adverb is saying. どうかすれば, どうかすると, ともすると, ややもすれば, and ややもすると are all synonyms. どうかすれば ("if things turn out in a certain way", "if something happens") may be the most intuitive form to grasp the nuance. If ともすれば is used with a habitual action, "to prone/tend to" would be an appropriate option. In your examples, ともすれば is effectively weakening the meaning of そうになる (i.e., 腰が抜ける is only an unlucky possibility).
