Is overthinking violate third precept? I have noticed most of the time third precept is interpreted as sexual misconduct or adultery. But third precept emphasize all the misbehavior and misconduct using all six sensual spheres. "Kamesumichchara" in here kama means involvement of all six sensual spheres.

E.g in this answer;  One must abstain from committing adultery or sexual misconduct. Romantic relationships that are emotionally or spiritually damaging to others, due to existing commitments of the parties involved, are a cause for stress and suffering and based on perversion of the mind.

My question is how fair or correct to narrow third precept to sexual misconduct or adultery?

Does over-thinking violate third precept because its a misconduct of mind due to uncontrollable and misuse mind?
In my (Mahayana) interpretation, Kamesu-micha-cara means "Behavior incorrectly motivated by desire of sensual pleasure". This pertains to any pleasure associated with any of the senses.

The core idea of the precept IMO is that "desire of pleasure" is "wrong motivation". It is not that sensual pleasure in and of itself is bad. It is that receiving pleasure is an invalid goal. Instead, behavior should be motivated by a valid goal, such as health, well-being, harmony, peace, and Liberation.

Since mind counts as one of the senses, any activity "motivated by desire of MENTAL pleasure" should count as violation of the precept. This would pertain to indulging in all types of mental pleasures such as idle conversations, games, fantasies, philosophizing and others. 

There is a fine line here though. An activity would only be a violation of precept, if its sole motivation was receiving (mental) pleasure. If activity has benefits such as development of mental faculties, reduction of pathological mind states, and increase of wholesome mind states, then it should count as constructive activity of useful nature.

For example, if someone is depressed, and is engaging in meditation aimed at increasing motivation and generating positive mind states, this should not count as indulging in mental pleasure - even though it involves deliberate generation of joyful mind states.

So I think the main criteria here is, whether we are indulging for pure pleasure, or doing it deliberately with a wholesome goal in mind. 

And yes, in this interpretation "overthinking" or more precisely "indulging in thinking and philosophizing for the pure pleasure of it" would count as violation of third precept.