You've got a lot of strange stuff going on in there! There is no need to edit product_listing.php for any of what you want. Better to put it back the way it was and do your styling in the stylesheet.
Of course, that raises the question "which stylesheet?" - stylesheet_new.css? stylesheet_original.css? stylesheet_woz.css? css.css?
You are using an old version (1.3.0.x) of Zen Cart, and really should upgrade for security if nothing else. All those stylesheets are interfering with each other. If you set something in stylesheet_new and it is defined in stylesheet_original, your new setting will be overridden since the last to load (in alphabetical order) controls in a given situation.
What's the deal with css.css? You appear to have copied a view source and named it like a stylesheet. That is a bad idea, as is making all of your edits in the /classic/ template folders, which means that when you do upgrade, all of your customization work will be erased.
And you somehow have the <head> section of your HTML page output intermingled with the body.
Now that I have thoroughly discouraged you, it is possible to recover from all this. It's going to take some work, though.
The first thing you need to do (after you delete css.css) is read up on template creation in the FAQs, and copy all /classic/ folders and their files to /your_template/ folders (whatever name you want), and edit template_info.php and activate your own template per the instructions.
You will need to upgrade to the current version 1.3.8a so you don't get hacked (hackers are out there all the time poking at Zen Carts for the vulnerabilities in your version). This will be a large job because you will need to switch from a table-based template to a div/css-based one, nevermind rooting out the weirdnesses in your files.
And finally (well, you can do it now:), edit your stylesheet_new and add
h3.itemTitle {height: 9.0em;}
Search all the other stylesheets for other cases of .itemTitle, and merge any you find into one place in stylesheet_new.
One shortcoming divs currently have compared to tables is that there is no way to require that all divs in a row have the same unspecified height. They have to be either independent, or explicitly given a fixed height.
This means that you can't just line up the price/add elements; you have to give the whole product or the individual parts of it fixed heights (greater than you ever expect them to need).
The .centerBoxContentsProducts div also has a .centeredContent class tag, which would make the elements inside all centered. Apparently some declaration in one of the stylesheets is overriding that for you. Find it and eliminate that part.
Good luck! If you can't find clear enough directions in the FAQs and forum threads, ask again.
