Link to Post ID to prevent broken links when updating page titles?

I am building a large scale website for the church where I work using Ultra Theme and Site Origin Drag-and-Drop Builder. I currently use Weebly for our church’s page, but it is not really powerful enough to suit our needs and the scope of what we would like visible and available on our website.

So, I have designed and fiddled with another site at domainname.org/wordpress

Now that the site is complete, I need to move it out of the “wordpress” file folder and into the top level. However, my biggest problem is that–as far as I can tell–every single link, except for my menus, has been hard coded with the URL, rather than a post ID. I’m thinking that once I transfer the site, every link is going to break–and potentially every link for images, too.

So my questions are:

1) Why won’t the regular link dialogue allow me to link to a page using a post ID rather than the URL of the page? Am I missing something? Is there a plug in that would alter the link interface so that it would link to a page/post ID? [I know this is possible, because the slider widgets will do it.]

2) Can I just set up an htcaccess file to “mask” the subfolder permanently? I know you can have the index file re-route to something in a subfolder, but what I would ultimately like to do is have “wordpress/” not appear anywhere in any urls that my users are typing in.

(For instance, the current site allows youth parents to go to domainname.org/youth and go straight to where they need to go. I would like to keep this capability.)

I hope this makes sense. I was a hobby user until I sort of landed this job accidentally, and now I feel like I’m in a bit over my head.