Learn English – ‘what would make you think that’ vs ‘what make you think that’

Though the complex preposition of off of is widely used, one may argue that it's redundant.

Here is the Oxford Dictionaries' reference:

Off of is often used in place of the preposition off in contexts such as she picked it up off of the floor (compared with she picked it up off the floor ). Although off of is recorded from the 16th century (it was used by Shakespeare) and is logically parallel to the standard out of, it is regarded as incorrect in standard modern English.

Now, about the point

someone got a point - someone got an idea to think upon

The dictionary you quote is perfectly accurate; "I would think", etc., is used in situations where you are expressing an opinion without being too sure about it. The difference between these two sentences is one of nuance:

I think he's about fifty.

I would say he's about fifty.

The first suggests that you have some grounds for your opinion, and the second that you're more or less guessing. See this earlier question for a further discussion.

It should be noted that you would think doesn't mean the same thing at all. If I say:

You would think that the bank could figure out a more secure way to allow customers to transfer funds between accounts.

what I'm actually saying is that the bank has not figured out a secure way to handle fund transfers, and that this is unexpected. Unlike I would think, which is in the nature of a guess, you would think states something contrary to fact.