How to show that the department fits my research goal?
Your draft paragraph says nothing specific about the department or lab beyond the "create a better world" vision statement, and it says nothing specific about you beyond that you can enrich diversity.  (Every applicant hopes to be a valuable asset and feels they have a compelling plan.)  If your paragraph were swapped with another applicant's, in many cases nobody would notice the mismatch.

I'm not convinced that's a problem.  Your statement needs a conclusion, and this is a conclusion.  Writing a better concluding paragraph will make at most a small change in your chances of admission.  If the rest of your essay is compelling, then this conclusion won't ruin it.  If it's not compelling, then the last paragraph is too late to save it.  If you have the time and energy, it could be worth trying to write the perfect conclusion (one that is specific to both you and the department), but you should keep in mind that this is a minor form of fine-tuning.


  Should I use this part to raise their emotions? 


I don't think this will be effective.  Reading statements of purpose just isn't a particularly emotional activity.  Usually, committee members are skimming through them looking for the important information and ignoring fluff, and anything that looks like an attempt to manipulate emotions will count as fluff.


  Should I use scarcity to raise their emotion?


I'm not sure I understand what you mean by using scarcity.  Are you talking about raising fears that you are a scarce commodity and they might lose you to another department?  That doesn't need to be addressed, and it can look like hubris.  Most applicants just aren't that unique: there may be dozens or even hundreds of roughly similar applications.  (Of course everyone is unique and special as a human being, but this uniqueness isn't necessarily apparent in or even relevant to graduate admissions.)  The failure mode is usually not "oh no, this amazing candidate is lost to us forever" but rather "oh well, let's accept a similar student who was almost but not quite as promising".

To the extent your application is unique, that will be readily apparent and you don't need to emphasize it.  To the extent it is not unique, trying to raise emotions with impressions of scarcity will look arrogant or out of touch.