Google not hit back to your website if you check ranking everyday but if you do the keyword stuffing again and again then this is of issue can be happen. You try the ranking check website to checking the ranking instead of search it from Google.
The worst that'll happen is that google will throw up a catcha when you try to search to make sure you're not using automated SERP checking tools. They will not penalize your site. A good rule of thumb is to ask if a competitor could easily do to your site what you're worried about. If the answer is yes then google probably won't penalize you for it.
No, google will not give negative point even if you check your site every hour.. One case: Some people have behavior to compare price for things that they want to buy. They compare from some sites, and open the same page for items every hours or day (although they dont realize the open the same page couple time) Will it make google give negative point those sites ? No..
No thats not true. Its just a myth. As long as you are following Google webmaster guidelines and doing good for your users, you are good in Google's eyes.