Drupal Question about Aliasing, Duplicate Content, Backlinks & Rankings

[PROFRBcom]

We use Drupal for our website. As such, each page is on a node when created. So lets say our latest article is domain/node/1067 - When we publish it, we give it an alias of lets say domain/online-pоker-news/XYZ-pоker-site/news-description. The page can be accessed from both URLs. We can also go in there and make an entirely new alias for the same page, say somthing like domain/omg-breaking-news-at-xyz-site. All 3 URLs lead to the same content.
So with the scenario here where there are 3 ways to access the content, I'm not sure what happens, how it works, and if we could screw something up by creating the 3rd URL.

The domain/node URL is never indexed/returned in search engine results if an aliased URL has been created. The 2nd URL, the aliased one created when the page is published, is the URL given in search. To further the scenario, the orginally published URL:

1) Has existing external (and a shit ton of internal that would be difficult to change) backlinks
2) Is already ranking in SERPS, but not as well as we'd hope.
3) Was very poorly constructed structurally, looks awkward, and is KW stuffed

What we DO KNOW:

If we create another alias for this URL but do not link to it onsite, but only have it in our autogenerated sitemap:

1) Google will pick it up and start ranking it in a handful of days.
2) Google will still be ranking the original URL as well (at least in the short term).

What we DO NOT KNOW:

1) If google will penalize us for duplicate content since one page has 2 URLs and both URLs ostensibly lead to the exact same content. (we're not sure if Google knows the difference?)
2) If google will count all those internal and external backlinks to the original URL for the new URL or if we are shooting ourselves in the foot by losing accumulated backlinks.
3) If it is a good or bad idea to create the new URL, which is the one we'd like to be shown publicly since it is cleaner, more readable, etc

Here is an example from our site where the original URL was no good and we created another alias.  As you can see, both aliases of the original node lead to the same content:

http://www.professionalrakeback.com/node/14
http://professionalrakeback.com/merge
http://professionalrakeback.com/Carbon-pоker/Rakeback-and-Bonus-Codes/Does-Merge-Carbonpоker-Offer-Rakeback

Any and all help appreciated!