V + 到。。。。头上来: Exact meaning and how to use?
This is a good question. First of all, 头 is the most important part of a human body. So, for someone to climb on top of another person's head 爬到 Subject 头上 or to ride on top of another person's head 骑到 Subject 头上 shows great disrespect to the person. This term is used usually to express incredulity on the action of another person.


Because this phrase XX头上XX is usually used in the literal sense,
any translation to English has to be done on a case-by-case basis.
到 always used together with a verb in front for this type of construction if you want to use 到 at all.
Yes, for example, 算在 Subject 头上. Note, 来 is not necessary here.
As explained earlier, 头上 refers to the most important part of a
human body. It still refers to whoever is the Subject, not necessary
自己 (yourself).
The following would be how I would translate the three sentences: a)
I should be the one looking for you to settle the score, but you
have come to look for me instead! b) They lost some stuff but ended
up investigating on a little kid! c) Your bullying antics have
gone on unchallenged, now you even dare to bully him!


Note that for the three sentences above, omitting the words 头上 would not change the meaning of the sentence. In English, it could only be represented by an exclamation mark as a way to express incredulity.

However, the more common usage would be 爬/骑到 Subject 头上 where 头上 is not optional. Example:


  婚前她千依百顺，婚后她却骑到她丈夫头上，百般刁难。 She was very obedient, but after their
  marriage, she rides roughshod over her husband, making life difficult
  for him.


The words 头上 can also be found in an idiom 在太岁头上动土, which means to do a daring act that would offend someone of higher authority.