Well it seems that it does work when I get pins 9 and 10 oriented properly. I don't know if this is good news or bad news.
I suggest that you rip everything out and start over with the modified Hello World sketch and verify that your LCD is still alive. If it is OK then try your version again. Then, if that works, we can start to clean up and restructure your code.
Absolutely nothing visual happens on my display
I started my troubleshooting by making the cursor visible although I don't normally run the LCD that way.
Don