I understand that most rewards comes from those few accounts and therefore rewards pool is bigger and other voters can also benefit more. Correct?

No, the reward pool grows at a finite amount for each group of blocks that are produced. Neither haejin nor anybody else creates more rewards through content.

It all comes down to the worth of a post. If a vote for yourself means your post is valued at .08, it is doubtful that many people will have a problem with it as long as there is some substance and effort put forth. If your self vote means your post is worth $350, people will look at that post a lot more closely in order to ascertain its worth. If you self vote every post to 350 and post multiple times a day, people will look even closer at not only your posts but your whole account and associations, along with your motives.

In any case, on this platform, the account holders themselves, as individuals, are responsible for determining post worth, and when accounts that upvote your post in robotic fashion to such high numbers (as those listed do) you can expect some opposition to that.