Re "I did all the necessary things prior to sending the file to a reputable online printer"

Did the printer send you ICC profiles for your computer/monitor? If not, it's a guess. If they are just requiring unspecified JPEGs, is your color space sRGB?

I've used Adorama Pix in the past and they have downloadable profiles. Only once when I was printing on metal prints did I feel the tones were off on a few of the files. They had me adjust and resend, then reprinted at no charge.

If you'll be doing image work, spend a bit more and save yourself the frustration. I would suggest something about 3 years old, many come off lease at that time and are being sold. Plus an imac with a larger screen would come in handy. I know my company has a lease end this year, and there are 2-3 systems we'll be selling, one is a 27" imac, probably won't be available until late spring though.

FYI - The info for your file identifies the lens as 28-85mm 3.5-4.5, with focal length of 34mm

Boys of Summer.

get all the RAM you can afford.
For the hard drive, 512gb is fine if you don't keep a lot of photos on your system. I have the 1tb ssd, and I still have to dump off images/graphic files off to external drives yearly.

I've downloaded some free ones, and also bought a free package. There's probably about 3 or 4 our of about 100 that I use, and sometimes tweak from there. Have started to delete the ones that I think are just awful.

I've been on a Mac since 1989, and I have to say, Photoshop can be a bit daunting to a new user, and you'll probably only use about 5% of its capabilities.
I'd suggest you look on your camera manufacturers web site, they usually have a program to download to process raw files. I shoot Nikon and they have a couple different programs, Capture or View, that are free downloads. Or try the other free programs others have mentioned. Would try all of those before spending any money.

I have the D7000 and have found the 85mm 1.4D to be nice for portraits. I've used this a couple of times as there is a rental place near me and they'll let me have equipment from friday noon until monday noon for a one day price. Here are some samples of a shoot I did at a local food bank last fall. A little more casual that real "portraits", but you can get a sense of the bokah. I see some think this lens is less than sharp, so I'd like to try the G some time. Worked well for this assignment which is for their web site only.

All were shot fully open, 100ISO aperture priority.

no, my son is the drummer that looks like he's 14, but tries hard to look older with that snarl on his face. I got to know most of the other artists though as they have all roomed together at one time or another, played in the same bands, or more often worked in the same restaurants. All a good bunch, chasing a dream, and smart enough to get an education in the process.

nice job. As a creative director, I always instruct designers to go over their layouts and ask themselves, which elements are not absolutely needed, then take a hard look at whether any fall into that list add or distract from the overall composition and subject. In this case, i think the yellow rule would fall into that realm. It's your book, but I'd suggest printing out a copy with and without, put it on a wall, then decide in a couple days which one works best for you.

nice job. As a creative director, I always instruct designers to go over their layouts and ask themselves, which elements are not absolutely needed, then take a hard look at whether any fall into that list add or distract from the overall composition and subject. In this case, i think the yellow rule would fall into that realm. It's your book, but I'd suggest printing out a copy with and without, put it on a wall, then decide in a couple days which one works best for you.

The Light the Nations Festival, in Nashville's "Nations" neighborhood. Seemed that much that could go wrong did. It had been 4 years since I've seen my son play live, so I brought some equipment, and arranged to rent a 70-200 f2.8. Lens rental fell through because of a delay in in my flight, so I was left with my cheap 35mm 1.8 DX lens, and managed to borrow a 50mm 1.8 that was slightly better. But I must have changed the setting on my camera from RAW + jpeg to just jpeg when I was downtown earlier in the day and never changed it back! Still had fun, and got some shots that are keepers for me.

Always back up your computer, you should have an external drive two times your internal hard drive size that is just running Tim machine i the background. Make sure there is a fresh backup completed before updating system software.

Also, consider dumping photos off the system to external hard drives. They're pretty cheap now, I try to keep two different drives that have the same files just for protection.

As others mentioned, the card may not be performing to a high enough spec, but the files may be fine. Try downloading them to your computer first. then try to open in LR from that location.

No need to have both monitors being expensive, color calibrating HD. Use a cheaper one for things like email, palettes, this forum, etc. Then use the large one for your image work.

I mostly use my laptop with the text screen being from that system and running a 27" display for image/layout work. Once in a while I have the need for more power, so I hop on a tower that was built for video editing. In the middle of doing large images for trade show graphics, so i do this with the 27" screen along with a small samsung for all the palettes etc.