Another option is to take an image with the iPhone and use its GPS data for the images from your Nikon. This works well if you're taking a bunch of photos from the same general location and then moving onto the next.

Are you sure you're losing resolution or is the camera just compressing the image more? Losing resolution would mean the pixel dimensions of the panorama are less than a single image.

If you stop paying for CC, you can still use the Library module to view, export and do some minor developing. You could also purchase Lr v6 as an $80 upgrade to v5. It's not easy to find on the Adobe site but it is an option.

Lightroom does not backup photos. You can, during import, choose to have a second copy made which could be thought of as a backup. When you close Lightroom, it should ask to backup the catalog. You should have it backup the catalog to a separate drive than your active catalog, that way if the drive fails, you'll have the backup to recover from. You don't have to have all 12K photos in the catalog to backup the images.

The pizza place opened in 1973. The movie was released in 1988. The pizza place, though not used for filming, still stands and they play the movie constantly.

You need to convert the raw files to DNG using the converter and then open the DNGs in PSE.

If you don't want to spend any $, you can use Adobe's free DNG converter to convert your raw files to DNG and then import the DNGs into LR4.

It takes a long time because the manufacturers typically don't provide any support so Adobe has to reverse engineer the raw files. Nikon decided to throw Adobe a bone and provided assistance for the D5 and D500 so they would be recognized upon release.

Double check that you're running Lr v6.5. You may be using an older version.

You can get refurb 5DS from Canon for $2800 or a 5DSr for $3000.

It's not that Nikon or Canon won't support their raw format in the future, it's that Adobe and other software programs may not support a raw format. The thought is that since each new body has a slightly different raw format (even though the extension is the same), the software developers will "drop" support for older cameras in order to "save space". For example, 10 years from now you may not be able to process a raw from a Canon 40D.
You may want to read the following opinion piece from Petapixel: Why I Stopped Using the DNG File Format

Maybe this video from Anthony Morganti will help.
https://youtu.be/YPOxfeyLtCI

Like you said, only a few cameras have this capability. Since I only own Canon cameras and they do not have the capability, I have not tested it.
Not sure if you seen the following:
http://improvephotography.com/34818/iso-invariance/

First thing I'd suggest is calibrating the screen. When you say "(supposedly) 100% compatible ink", does that mean you're not using Canon-branded ink but instead using a third party? If so, have you tried printing the same images with Canon ink? There are enough variables which could be causing the issues.

Is your screen calibrated?