Because of the definition of what focal length is. From a Nikon site: "The focal length of the lens is the distance between the lens and the image sensor when the subject is in focus, usually stated in millimeters (e.g., 28 mm, 50 mm, or 100 mm). In the case of zoom lenses, both the minimum and maximum focal lengths are stated, for example 18–55 mm." It does not describe the size of the sensor. The concept of "equivalent" as a description relates different sized sensors, to a sensor sized the same as a 35mm film image--which was a common size when digital photography was introduced.

In other words, you do the same calculation with all the lenses, even the EF-S lenses.

Although I understand, from my own experience, the blinders that come up when the idea of a new computer comes to mind, you could check into expanding your computer memory to whatever is the max capable for your existing system. That is the bottleneck you are experiencing. I went from 8gb to 16gb in a 3 yr old Lenovo i7 laptop, and it made a tremendous difference running PS and LR and processing multiple images. So whatever direction you go, don't scrimp on internal memory. If you don't already have one you should also get an external monitor, and get a calibrator that will do more than one screen. Fact is, no laptop will check all the boxes fully when it comes to photo processing.

Note that the camera connects to your wifi network, not directly to your computer. IIRC, there is a specific manual that describes how to set this up. Although there are other uses for connecting the camera to a wifi network, the wifi feature for transferring images to your computer is interesting, but quite underwhelming speed wise. I used it a couple of times, but went back to transferring images via USB cable, as it is at least 3x faster (didn't make any measurements). My preference is to move images this way, rather than removing the card from the camera each time and using a card reader.

I use a hand strap / shoulder strap combo, purchased on Amazon. Use it on a Canon 80D. Should work with your Sony. The products are a $20 WITHLIN Professional Photography Swift Sport Shoulder Strap (Strap +tether +plate), and a $9 Case Logic DHS-101 Quick Grip (Black). I did not use the twist knob that comes with the hand strap, but instead attached the bottom part of the hand strap to the slot in the WITHLIN attachment plate. When carried in the bag, I remove the shoulder strap (unhook the locking carabiner)--but this decision has more to do with the way my main bag is configured. I leave the hand strap (and the safety tether) attached to the camera all the time.

You can find all kinds of great printers for less than $400. The manufacturers get you on the back end on ink, as you probably already know. Unmentioned in your post is what you use the printer for, since you are replacing an all-in-one. Pixma Pro series is great as long as you have the space (which it sounds like you may not), and understand it is JUST for printing photos. If you want a scanner, or to load it up with copy paper for everyday printing, you need something else--either entirely, or in addition. If quality photo printing is what you want, then look at printers dedicated to that task--with the idea that you would never run anything other than photo paper through it. At $400, you might well be able to obtain two different quality devices. Also, you may be able to rethink your "limited space" requirement, since most printers are wireless, they don't have to be in the same room anymore.

Looks like a rollover, with the driver door torn off post accident to get in the vehicle.

The advice you are getting is sound.

I was not prepared for the sheer mass of the Pro 100. It is really heavy, and its footprint is nearly four times that of my Brother all-in-one laser. Closed it is 27x15x8.5 inches (LxWxH). With the paper feed and output trays deployed, add 21" to the W dimension, and 6" to H (without paper). Does a great job with color print. If you will never want to print on anything larger than 8.5x11, there are other good options available.

It is not the most cost effective way to print photos (even large ones)--just like having a darkroom in your house wasn't the most cost effective way to make prints in the old days. For me, I like the idea of making the photo--start to finish. Even if it won't be as good as that from a professional lab. It's not a decision based on economics.

A decision that is based on economics: keep (or replace) your current printer for general printing. Cheapest general printing is going to be a B/W laser. Even though laser cartridges are more, your per-page cost is approximately 1/3 (or less) with a laser.

Use the rebate for the Pro 100 if possible.

I don't think you went "wrong," but you might not be done working on the images.
Was the second shot yours, or after the IG filter was used?
I personally like the pose in the second shot more, because my eye is drawn to the same place as hers, the baby bump. She seems contemplative. In the smiling photo, her face is more the focus, and it is too dark (there are some remedies for this in post most likely). For future reference, one thing to experiment with is a reflector to put a bit more light on the front.
Try a different cropping --moving her a bit more to the right in the frame, and see if you like that. Or more importantly--if she likes it more.
Congratulations!

If upgrading from what you have is your goal (as you said it was), then you have made a good decision to go with the 80D. The biggest thing you will notice immediately is the upgrade to the auto focus system. The touch screen is also a feature that will make you feel spoiled.

All the lenses you used with the t3i will work with the new camera. If you don't already have it covered with something better, then the 18-135 kit lens that comes with the 80D is a pretty nice lens for the money.

There are a lot of bells and whistles for various ways to customize your image if you shoot jpegs. Beyond playing with HDR, I don't know much about them other than what I read in the book, since I shoot RAW almost always.

Since you are waiting on the refurb to come available, in the mean time download the manual and read through it. There is a lot of cool new stuff waiting.

Look into borrowing a calibrator. Maybe you can rent one. Although it is recommended that you recalibrate every month or so, the change made during the initial calibration is usually pretty noticeable, while the subsequent changes are fairly small. I use a laptop screen and an external monitor as a dual monitor setup, and having them nearly identical has been great for my work flow.